What does it mean, and why? I was looking at several lexicons, but didnot find a satisfactory explanation.
I have found this (thefreedictionary.com):
Proverb: You do not need more than enough of anything.
We don't have much of a surplus of food for dinner tonight, but enough is as good as a feast.
Jane 1: I wish I could offer you more lavish hospitality.
Jane 2: Don't be silly. Enough is as good as a feast.
(British old-fashioned) Something that you say which means you should not have more of something than you need:
No, thank you, nothing more to drink for me. Enough is as good as a feast.