After hours?!
Question:
After hours?
what motivates you after work from being tired?
Answers:
plan it into your day just like you would dinner with a friend or a doctor's appointment. It's not negotioable. Also, it helps to not go home first - go straight to the gym/pool/track from work.
Also, think about how great you'll feel after, and the next day. have you EVER thought "man, I shouldn't have worked out" after a work out??