I have found that one thing that helps me get back on track with exercise is getting something new to work out in lol Whether it's just a new pair of cool socks or a sports bra or a new pair of capris - I have found it does the trick. I can't wait to wear whatever which means i have to work out. lol Buying the smaller sizes seem to help too!
I am sure others have "tricks" that help them get back on track or stay on track!