My heart and my commendations go out to all of you who rescue, trap and foster these poor kitties. You are much stronger in character than I.
You are doing something that is completely selfless and wonderful. Who knows what the cat situation would grow into without you. You all are angels and have definitely earned some big beautiful wings.
Try not to let it get you down...look at your success stories when you start getting frustrated and remember, love is why it is you do it.