The flopYour conduct in the second round of betting is decided by how well the flop fits with your starting cards. If your hand does not fit the flop you, you should consider to fold. "Fit or fold" as the American expression says.
Of course, you take into account other factors, but the more who remain in the pot, the greater the risk that someone else has a hand like a better fit with the flop than you do.
However, if you have joined the flop and you think that you have the best hand for example an overpair, tops, two pair or trips. It can drive out those who might otherwise stick around and take a chance on getting a flush.