how do you keep cool and not take things personally

This is a tough one for me to answer competently, as I largely overcame this problem at age thirteen in a less-than-conscious way, and you're having to swim upstream against a backlog of neurological ruts worn three decades deeper than what I was up against at time. But, that disclaimed, for me as an adolescent, it was a sudden epiphany one day that other humans' impressions of me do not actually carry any real effect, and that it was very strange that I had ever thought of them as something I should obviously be interested in. Except to the precise extent that someone is willing and able to actively disrupt your life, their impressions of you may as well be birdsong or dogs barking.

The words may convey one of many easily-understood perspectives that could be taken on the whole issue, but how to get from understanding the idea to "deeply realizing" it and living on the basis of it is a whole other matter of course, if that's even the route you'd want to take. For me, the transition was virtually overnight. The only other thing I could say is that this doesn't so much entail the cultivation of a new point of view as the abandonment of the one you have on the assumption that it wasn't fulfilling any particular purpose, and nothing needs to take its place. It's not working to overcome the anxiety, but ceasing to do the work you've been doing to sustain it. This will, of course, give you whole new problems in relating to others, but you've been accustomed to loneliness so long by now that it's unlikely it would lead to you being hurt in new ways.

If I’m quiet there’s a problem. That means I’m done and i can’t be bothered anymore. If i shoot my mouth off I most likely am hurt but whatever I say is the truth and may even contain things I really think or feel and I don’t care what happens.

I have a saying that helps me cope with how others behave and interact with me.

It's better to be understanding than understood.

If I gain insight into the motives of others, I can guide myself to not take everything so personal.

What you'll find Is that other people and their intentions/motives are very egocentric, and rarely are they an outright attack on you.
Making it much easier to dismiss their nonsense.

It may not make it right from their end, but atleast you'll know that it's not about you...but that it's about them.

You use all the help the NHS has been giving you for years, especially making the most of those anger management lessons you attended, take some of the advice you have been offered for years on various Q&A forums/sites and start listening to what your parents have been telling you for years.

Also you might want to stop feeling sorry for yourself and stop endlessly shitposting on websites like this, year in, year out. Turn your PC off, get out of that council House flat you never leave and get a job.

I struggle with it too but from the moment I realized that it's probably me and not them it's getting better.

One advice...try to turn every offense, or a thing that you personally find offensive even if it wasn't meant that way, into a joke and laugh it off. If the person intended to offend you, the expression of confusion in their face when you give them a completely different reaction than they expected is quite rewarding.

Thats normal. Just dont take what they say to heart. You deserve to be happy

I honestly just don't give a fuck, so it's easy for things to go in one ear and out the other