For me, it was the results.
The first 4-6 weeks of exercise were tough, but I held to it. I just had to stick to it and promise myself I wouldn't bail.
After 6 weeks, I noticed my at-rest heart rate had dropped 5 bpm and it took A LOT more stress to take my heart rate above 160. In order to get above 160, I REALLY have to push myself now.
In addition to that, my legs are beginning to become toned, the muscle is still as large as it was before, but now its much more tight and has a great shape.
A couple things that helped me stay motivated:
1) Exercycle is placed right in front of the TV. There's no excuse not to ride it while watching the news or my favorite show.
2) I taped my before picture to the console on the bike, when I feel like quitting early, I look at that picture, say 'No way in hell' and start pumping harder.
3) I scheduled my work and sleep schedule around it. I used to wake up at 8am to get to work by 9am. Now I get up at 6am to get to work at 8am. I get extra time to work out as well as getting out earlier from work to work out again before dinner. This may not work for you if you don't have a flexible schedule. My boss was very supportive though.
4) If you live with others, put the exercycle somewhere that they can see you exercising (if its not too loud). I found myself using it more often, because I knew if I didn't, THEY would know I didn't. Its easy to tell yourself 'eh, I'll do it tomorrow', but then when someone asks you why you didn't work out today, you don't have a good answer