... the healthy person, the healthy in body and spirit, is a person faced with many difficulties. He has a lot of problems, many of which he has deliberately chosen with the sure knowledge that in working toward their solution, he will become more the person he would like to be.
Part of the art of choosing difficulties is to select those that are indeed just manageable. If the difficulties chosen are too easy life is boring; if they're too hard, life is self defeating.
The trick is to move oneself in the direction of what he would like to become at a level of difficulty close to the edge of his competence. When one achieves this fine tuning of his life, he will know zest and joy and deep fulfillment.
This seems right to me—not just for life in general, but also for research and thus note-taking.