As everyone else has said - don't use your own energy but use the universal energy. You can channel & guide it through you without depleting yourself.
Another thing I do when doing energy work is put up protection, or a shield (for want of a better expression) - I see it like a filter- probably a better term - that allows good energy in to me, and through me, and also lets it flow back out, plus keeps out anything I don't want, and protects against my own energy being drained. Set your intent that it is for the good of all - that's including you.
not sure if that made sense :s baby brain big time here! HTH