According to Aristotle, pleasure is not a process but rather an activity. For every process aims at some end and is complete only once it has reached this end, but pleasure is complete at any time and has no need for anything else to complete its form. Pleasure is a whole, and hence has no coming to be. Pleasure is choiceworthy in itself, the same way that the state of happiness is an end in itself.
Pleasure, however, can be seen as the completion of an activity. Not in the same way as the state does, but more as a kind of consequent end. Since pleasure completes activities, and hence completes life, which is desirable, it therefore makes sense to say that people aim at pleasure because it completes their life, which is choiceworthy. Pleasure is proper to the activity that it completes, and thus increases it. In this way, we judge each thing based off of its relationship to pleasure. Since pleasure increases an activity, we are more inclined to improve or excel in an activity which we find pleasurable.
I find this to be quite true, as I have succeeded most often in activities which I enjoy. Activities which I find less pleasure in are typically the activities in which I do not excel. This goes especially for subjects of study, as well as sports. Subject matter which I find to be interesting is more likely to result in me coming to a greater understanding of it than that of a subject in which I do not find interest or pleasure. This is why it is important to pursue a career for which you are passionate because this is the work by which you will most likely find the most success.