If you are playing pretty standard suited cards according to the SSHE chart you should generally be drawing to a high flush that will hold up more times than not. As long as the pot odds are close you should hang on to these hands.

I believe you want to raise and re-raise with your flush draws on the flop and turn to try and get rid of lone high card hands which would beat your flush if the board 4 flushes. I also believe you are raising these draws for value for when they do hit, don't worry about keeping people in the hand, they will usually stay.