It's not easy. It's a skill you'll have to practice for the rest of your life. Still, recognizing the need to do it is a massive step, since most of us accept anxiety as the background noise of everyday life (to the point where we actually get confused when it's not there, the way city folk get freaked out by natural silence when they try to go camping). This technique requires you to regard your own peace of mind as a precious resource that is under continuous assault, and to reflexively defend it. A sort of martial art of the mind which involves strategically deploying or withholding your shit-giving as needed. I call it Noshitsu.