Peter Drucker:
The first step toward effectiveness is to decide what are the right things to do. Efficiency, which is doing things right, is irrelevant until you work on the right things. Decide your priorities, where to concentrate.
Work within your strengths. The road to effectiveness is not to mimic the behavior of the successful boss you so admire, or to follow the program of a book (even mine). You can only be effective by working with your own set of strengths, a set of strengths that are as distinctive as your fingerprints. Your job is to make effective what you have — not what you don’t have. (From Managing the Nonprofit Organization, 198.)