Oh boy! That's the million dollar question, isn't it? Medication helps. Guided meditation can help some people but overstimulates me. Tai chi can help. Tapping can help. Distraction and stimming help me most of the time. Look up a couple lists of coping mechanisms and take a shot on the dark. Eventually something might stick. Good luck!

Honestly I would say just keep trying different things and see what works best for you. Everyone is different so something that works for one person might not work for another and vice-versa. For ADHD I had to develop my own strategies for timing myself. For example, instead of using a traditional timer, I got into the habit of using YouTube timer videos with rain sounds and playing my favorite music at the same time while doing work. I also learned that I'm someone who needs to see things written down. I'm not good at using digital reminders like online calendars or note taking apps. I need a physical calendar and to write things down by hand in an actual notebook or else it doesn't stick to my brain. Set small goals for yourself and focus on baby steps. Remember that ADHD can make things hard so anything you're able to accomplish is worth being proud of and celebrating. :) You're doing better than you think, so give yourself some credit for trying. Anxiety has been tough for me too and again, different things work for different people. I do think that it helps to sit with your discomfort instead of constantly trying to fight it. When it comes to catastrophic thinking and imagining the worst case scenarios, I try to reframe things. Like instead of thinking "What if this event goes wrong?" ask "What if it goes great and I have fun?" you know? But also remind yourself that no matter what the outcome is, you will be okay either way. Even "bad" outcomes aren't the end of the world. You've been able to get through difficult times before so you'll be able to do it again. Don't give up on yourself. Good luck and hope you can figure out what works for you soon!

Try hypnosis or try emdr.