I've found mindfulness meditation to really help with panic attacks and depression and especially ADHD. I find that when things feel overwhelming or when it's hard to focus or you have thoughts and emotions that spiral too much one way or the other, it can give you a chance to wipe your slate clean and start again. Kind of like how sometimes you have to restart your computer to fix something that's gone glitchy.
Also if you have panic attacks you can take care of it more "discreetly", (or prevent one all together) which is an important skill to learn, as in some places (like a lot of work places) they don't just let you take "time outs".