In fact, doing the thing usually puts you in the right mood to be doing it. I learned this when my uncle moved from Boston to New Jersey. Before, he was a 45 minute drive away. Now, I’d have to travel at least 4 hours to see him. I regret that I hadn’t gone to see him more, even though I didn’t always feel like it.
This idea applies to exercise as well, at least for me. Often I just don't feel like putting on my running shoes and hitting the pavement. I can make a lot of excuses - it's cold out, I don't have time, whatever. But once I'm actually running, it feels good and I'm glad I did it.
One of the ways I motivate myself to exercise is to mentally picture how good I'll feel after. I imagine the "clean" feeling my body has and picture myself going through the day with increased energy. This method isn't fool-proof, but it definitely helps a lot.
What do you do to get beyond not feeling like exercising?