I'll be talking a lot about this topic and the topic of getting back on track in the next few months. Below are some helpful, inspiring and interesting articles and blog posts that I found today.
http://www.lifehack.org/articles/lifestyle/15-tips-to-restart-the-exercise-habit-and-how-to-keep-it.html
http://zenhabits.net/how-to-get-back-on-exercise-train/