Incentives to continue an activity

Sometimes when I am happy to do computer programming for an extended period it is because I ongoingly know what the next step is and it will not be long before I see its outcome. The steady, tangible progress is rewarding. This reminds me of when I first started working out on the cross-trainer: it was not difficult each day to exceed my previous day's effort level so that was another case of clear progress arising from moderate incremental effort. Now my exercise is instead at the point where each time I hope not to backslide further.