Check all the small stuff and see what you can do there. I swear by vitamin D3 for cutting down my mood swings. For some people sleep might be the issue, or noise pollution, or any number of persistent modern life issues. It all adds up, and you can usually track improvement by logging performance at e.g. fitness.

Also, if you haven't yet, read Enchiridion, one of the original Stoic texts. It is very much about what to do about this kind of stuff.