Harvard Business Review:

“Peter,” my friend Byron emailed me a few days ago. “I haven’t been diligent about working out over the past five years and I’m trying to get back in the gym and get myself into a healthier state. I’ve found that on my quest for a Mind, Body, Spirit balance, my body has been neglected. I need to fix it, and it’s VERY hard for me to get motivated. Any insight?” It’s the kind of question that’s on many of our minds in the midst of New Year’s resolution season.
  I really identify with this. Just need to do things and stop thinking.