Yesterday a wise reader wrote in to Ask Amy in the Chicago Tribune...
... Something valuable I learned is that you can only give of your excess. If you give to others from your essence (that which you need to keep yourself emotionally healthy), it will create a vacuum in your own life.
That vacuum will fill up with all kinds of negative things--resentment, frustration, substance abuse, etc. Giving to others is a beautiful and satisfying thing, but only if you can afford to give it.
-Learned the Hard Way