I just get obsessive. That is my going crazy. I am more of the achilles heel type people have mentioned if I am just angry at a person, but I tend to step away from that anyway because of the guilt that I would feel. They have to really deserve it. However, a friend of mine that tested INFJ (though I had assumed she was a mistyped ISFJ because she acts very differently from me - perhaps it's the other way around - well, I'm not an ISFJ but I could be an INTP or something?) tries to cut other people down. It seems very obvious to me how she's doing it. The weird thing is, she usually asks me about other people and I'm usually the one that encourages her to do a little subtle cutting down if people are being twats. She seems to cut people down if she feels they are getting above their station, rather than them actually hurting others. It's more that if someone says something quite arrogant she will make sure they realise that they are not that good by subtly pointing out their flaws. Perhaps that is more ISFJ of her because it's more about people not getting too up themselves (but being otherwise good people) rather than people actually hurting others. Dunno, some answers here just reminded me of her.
But yeah, I get obsessive and overanalyse, think too much, can get myself into a real state of madness. Self-absorption because I can't work out what's wrong and it bothers me so I end up thinking and talking about it all the time, trying to find the answer (and always failing seeing as often it isn't as simply as that). I get obsessive, my thoughts race, I feel endlessly frustrated and unhappy and then eventually burn out. Often end up not sleeping, sometimes to a severe degree (and if I am extremely sleep deprived I can start to lose judgement, which makes me hate myself even more). I never shout. I have raised my voice once in the last few years and I couldn't stand the guilt afterwards. This is more an enneagram one thing than an INFJ thing though.
I very rarely lash out at others, but this again, has to do with avoiding guilt and also has to do with my state of mind when unhappy - if I assume that I must suffer for my bad deeds, then no one else should suffer. See what I mean? If I believe that the most important thing is for me to be punished, then I would believe it to be immoral that others are punished. That tends to override any anger at others and be turned in on myself. Even if I can tell that others have done wrong to me, I balance it against my mistakes and assume mine are far worse, thus more punishable, and tend to prioritise that way. This just tends to perpetuate the unhappiness, though, which has an indirect effect on other people anyway since I eventually become too needy and a burden. So my own skewed logic never works out for the best.