Below is a link to an interesting article about Lance's return to racing written by one of his team mates. Bottom line - Lance simply loves cycling. The closing statement:
"On a bike, riding alone, in that environment, I feel at peace and can escape. Pushing myself in training to attain new levels, I feel the rhythm of the pedal stroke, the spinning wheels, my breath and the ticking chain. My mind is focused as there is clarity making me content. In retirement, I bet Lance missed that as well."