I will be discussing trigger/content warnings and explaining what they're for and why they're necessary. In so doing I will be naming some common triggers and talking about triggering experiences.
This needs a little bit of context so stay with me here.
I blog on Tumblr sometimes--it's my asexuality-specific blog if you want to follow me there, though I do occasionally post personal content. Now, recently Tumblr rolled out a site update that drastically changed a few things, and as per usual, some people screamed about it and some people enjoyed messing with it. Now that the posts on the Tumblr dashboard have no borders, it's possible to do very weird things, like make the dashboard look like it's falling apart or bursting open to reveal a scary thing. Some of the more sensitive users or users with sensory processing variations are saying it makes them very disoriented, and have asked people to tag their "bluespace" to help prevent this. (Some Tumblr users blacklist certain tags so they won't be shown content that is upsetting to them.)
Inevitably--inevitably--people who don't want to bother with tagging such things roar back, insisting that they should not have to think about these things and that those who have the sensitivities are responsible--entirely--for avoiding the content if it hurts them. These kinds of comments are also usually laced with denial that the content DOES actually hurt them--that people claiming to be triggered by descriptions/images of blood, mentions of rape or murder, or gaslighting that might remind them of their own experiences are actually just whiny-babies, trying to make an issue where there is none. So not only do they say it's not their responsibility to protect more sensitive Internet denizens, but they also claim it's not actually hurting them at all, no matter WHAT they say.
That, to me, is a big problem.
FIRST: Triggers and visceral reactions to disturbing material are real. If you have never experienced a panic attack, a flashback, a PTSD-type response, or a triggered dissociation/severe anxiety/etc., then good for you--you're fortunate. You have no business telling people who do experience these things that they're being babies or inventing their symptoms, and even if said symptoms were not as severe as they seemed, were entirely psychological, or were "just" emotionally upsetting rather than measurably physically damaging, you still have no business shaming people for experiencing them or claiming to.
It's extremely common for people who do not have disabilities to condescend to those who do have disabilities and tell them to their faces that their chronic illnesses, pain disorders, diseases, or other conditions aren't real or aren't as bad as they say--as if their idea of fun is inventing an elaborate story of personal suffering. If you're doing this and suggesting their difficulties and challenges are actually about limiting your freedom, do you have any idea how disgusting that is--to make someone else's challenges all about you?
SECOND: I see a lot of hollering about how people with problems shouldn't be able to force you to blah blah blah, but guess what? They can't! They have really no social power to stop you, and they know it. They ask you to help them have a more comfortable existence and make the spaces they enter safer for them. They ask for your cooperation, but as you've so expertly demonstrated, they can't make you. If your reaction to "please be mindful of people like me" and "please make one small effort to make my life less painful" is to go red-hot and scream about your own freedoms, you are missing the point and not processing what the requesting parties are asking for. Do you know what your failure to comply does? It makes their lives a lot less "free." You are saying that people who live with a condition or a sensitivity to a trigger are hurting you by asking you to hurt them less.
And it's pretty common for people who don't want to have to think about these things to take requests for trigger warnings as criticism of them as a person--as if it's a shaming technique to make them feel bad, not an attempt to improve their own lives or the lives of people they know. I shouldn't have to think about those things because it doesn't affect me! sounds remarkably selfish when the people you're ignoring have no choice about whether those things affect them. They'd like a chance at freedom too, and if you know about a common trigger (or a less common one that affects someone who crosses your sphere of attention), it really isn't asking much of you to adjust your behavior in one tiny way so another person won't have an unexpected, possibly immensely stressful and possibly physically damaging experience that can certainly ruin their "freedom."
THIRD: Another common snotty response to requests for trigger/content warnings is Well they can't expect to be babied online; out in the REAL WORLD there are no trigger warnings, so get over it! I've got to say here that yes, they're right; the "real world" is full of potential triggers, and it's much more difficult to control exposure to them when you have no filters. Guess what that means? It means that some people with severe triggers literally cannot leave their homes. Also, some people have disabilities and illnesses that allow them very little exposure to the outside world, and some of them are able to experience entertainment, social interaction, self-improvement, careers, and creative opportunities primarily because the Internet exists. If these folks' online experiences can be derailed and destroyed by content or media that makes them suffer, they may decide it isn't worth it to go to that site or enjoy that activity, and yet another thing is taken from them. Simply because some people feel it is too much work to put up a "Caution: Wet Floor" sign.
It is, again, incredibly selfish to say that you--a person who doesn't have to experience these things--need to be granted the utmost freedom to say whatever you want and post whatever you want because free speech and suck it up, when we are talking about actual people here who already don't have your freedom to move about in this world unchallenged and oblivious. They have to think about their triggers and how to avoid or tolerate them all the time, so hearing that you're not willing to help make spaces just a little safer for someone who's asked you to betrays an awful degree of entitlement and failure to empathize.
SO WHAT DO WE DO TO NOT BE THIS KIND OF JACKASS? Obviously, first, if someone asks you to post a content warning or trigger warning on something you've posted, go do it. You can make it part of an introduction and/or put it in tags if you're on a blogging platform like Tumblr. If your blog or platform has a standing trigger warning for a particular type of content, you can put it at the top as a blanket warning to anyone who comes through. Do your best to remember to tag that trigger in the future anytime you post about that subject. Secondly, learn the most common triggers. If you have flashy GIFs, warn for them. If you have violent or sexual content, discussion of rape and harassment, descriptions of abuse, slurs (racial, sexual, orientation-related, disability-related, etc.), self-harm and suicide, or gore/blood/puke, you should warn for it. Some people like you to warn for foul language or swearing, which may be more or less appropriate depending on your platform. Less commonly, some people like you to tag/warn for food (especially close-ups of meat), or unreality, or holes (trypophobia is more common than you think!), or guns, or drugs, or spiders and snakes and bugs, or skulls/death, or explicit but not erotic descriptions of sex, etc.
And lastly, if you're still scoffing, thinking it doesn't really make a difference because we'll never get everyone on the Internet to jump on board with trigger warnings so you might as well not worry about it yourself, consider this. Remember the starfish story? If it's your content that would have otherwise triggered someone and you are able to prevent this, that's one less horrifying experience in someone's life, and maybe one more day that contributes to possible overall healing. And when you offer trigger/content warnings, you also make other people aware that they can be necessary. You create opportunities to have this conversation or to inspire others to search for what triggers are and why warnings are important. We shouldn't just shrug our shoulders and claim that since we can't wipe out diseases entirely, we might as well not vaccinate anyone for anything.