A big, big thanks to Peter for passing this along.
"Whenever a Jesuit priest or a Calvinist pastor does anything of significance (for instance, making a key decision), he is expected to write down what results he anticipates. Nine months later, he then feeds back from the actual results to these anticipations. This very soon shows him what he did well and what his strengths are. It also shows him what he has to learn and what habits he has to change. Finally it shows him what he is not gifted for and cannot do well. I have followed this method myself, now for fifty years. It brings out what one's strengths are - and this is the most important thing an individual can know about himself or herself. It brings out where improvement is needed and what kind of improvement is needed. Finally, it brings out what an individual cannot do and therefore should not even try to do. To know one's strengths, to know how to improve them, and to know what one cannot do - they are the keys to continuous learning." -Dr. Peter Drucker
Related article: Managing Oneself - by Peter F. Drucker