I don't know if this will help or not, but what has finally got me to commit to fitness is just really paying attention to how I feel when I exercise vs when I don't exercise. There is absolutely, without a doubt, a 100% correlation between exercise and mood for me. Now that I've finally put two & two together (at the age of 40), it's so obvious.

Now, if I'm having a really bad day, wanting to cry for no reason or feeling down and wanting to stay in bed all day, my husband will say "when's the last time you got out and got some exercise?" It's worst in the early spring and early winter for me - when I'm between cycling and skiing weather. Hubby actually went out and bought me a Wii Fit to cover those two time periods, for his own self preservation.

Instead of committing yourself to becoming a great and wonderful cyclist again, or committing to losing 50 lbs, why don't you try just treating yourself nicely? Don't look in the mirror, don't step on the scale, don't keep track of your speed or mileage. Don't push yourself. Just go outside and have a little fun on your bike going whatever speed feels good for as long as you want to go, and pay attention to how it affects your mood and how you feel about yourself. If you keep doing that, pretty soon getting exercise will become a nice thing you enjoy doing for yourself. Once you're really enjoying it again, like you used to, then you can start pushing it but don't lose track of the fun.