How bad before you muck a good (great)hand??

[Pockets]

When you have the middle or low end of a flush, str, ful house,or just 2 pr, when do you save your money and fold? Aces on the brd, and you a pr.of 2's, what do you do, and when? 4 flush on the brd and you have jack or maybe smaller, when do you muck a made flush?

Any ideas on this for a full table / short table?