best is the enemy of the good
Prov. If you are too ambitious and try to make something better than you are capable of, you may ruin it. Bob: After I revise it a few more times, my novel will be the best ever written. Alan: I don't think you should revise it any more. Remember, the best is the enemy of the good. In fundraising as in other areas, the best is the enemy of the good. If you ask someone for a larger contribution than he can possibly give, he may give you nothing at all.