I have adopted cats that I have fostered. But I would believe it varies between organizations.

How do you let go?
1) If you don't you may not be able to help the next cat in need.
2) It is your JOB.
3) You cry a lot. First tears of saddness and then tears of joy.

Why do I love fostering?
1) I can help more cats than I could if I only adopted, because we all have a limit on the number of pets we can afford to have.
2) I get to have new faces around ALL the time. So it keeps life interesting.
3) I get to hear all the love that comes from the new parents as they raise their new kitty and know that if it weren't for me that kitty might not have even lived.