Via Sirus a translation by Brother Kenney of a letter of St. Thomas Aquinas to Brother John on how to study.
One point that keeps surfacing for me, and one that is so very difficult to gauge:
Do not spend time on things beyond your grasp.
How do you know if it is beyond your grasp until you've tried to grasp it, and by then you've already spent so much time on it that it seems a shame to give it up.