For me it was getting sober and specifically the serenity prayer. I have a terrible temper. Like break things and punch people temper. It’s always embarrassing to lose control like that. Well, saying that prayer reminds me that there are things I can control and things I can’t. Serenity is understanding the difference and accepting your powerlessness over things like the past, other people’s thoughts and actions, and even your own flaws. I am so calm now, I just have a “not my circus, not my monkeys” attitude most of the time. Occasionally, something starts to push my buttons and I have to walk away if possible, but that’s rare.
Also, make sure you’re getting enough sleep and try cutting out caffeine. Anything that causes more cortisol production is going to stress you.