I too love really physical regular exercise but just can't get it in regularly with 2 young kids either (oh, bygone days of kickboxing DVD's with Billy Blanks) much less peaceful meditative yoga (
What I do manage to get in to help unwind:
I take a bath or shower with favorite bath/shower things, come out feeling clean, make some pressed coffee and sit down (hopefully with a cookie or baked something) and watch a House episode from the dvr (kiddo sorta likes the show, so she'll tolerate that - sometimes set up art stuff for her first). I do this a lot, once a day, usually in the afternoon.
I used to make lists a lot - I've been trying to get back to that, it helps a lot of my anxiousness about 'what do I have to do, how will I fit it in, how am I going to do this'. I do this at bedtime while nursing (or at the tail end of nursing) and it's 'boring' for the other kid so she'll fall asleep while I'm doing my lists too.
I love baking and cooking, but since kiddo has become interested in doing it together, it's immensely less relaxing (but I've sorta focused on improving and trying new recipes a lot as a personal goal - doing it more reguarly has helped my confidence a lot because. . .ahem. . I am now easily really good
as evidenced by the deliciousness of the stuff I make, and few things that have really flopped.)
I use music a lot too, bringing particularly meaningful songs along in the car or playing them while hanging around doing bedtime stuff. If I'm feeling badly about myself or things going on, I'll just let myself feel that way through that song for awhile and then walk away from it.