I do the muscle thing before falling asleep too. And controlled breathing helps too.

Usually during a sever anxiety attack, my muscles are trembling, so I try to relax those by sqeezing all the muscles really tight and then letting go. It stops the trembling for a moment or two and for that time, my mind kind of clears.

Also I can't breathe during an attack so consciously trying to breathe slowly and deeply sometimes helps.

But when I'm just having some anxiety, I just watch a movie or listen to music/sing to get my mind off of any triggers.