Hypothetically, you're in a game with 5 other players at the poker table. The hole cards have been dealt and you take a look: Jh3h. The pot is $ 15 after the blinds. The 3rd and 4th position fold while the last player calls, you follow, making 35 $ total.
The flop is: 9hQdQh. You'll have a great time to draw a draw draw (~ 35%) and it will be Jack high (technically, Queen high.But everyone else plays that card ...) You watch the action: the SB bets folds, BB bets 40, the last player folds, and the ball is in your court. Do you call or fold?
Gut reaction is call; your chances of completing a flush are decent, and there's an outside (real outside) chance of completing either a straight or a straight-flush. Whilst it's true that other players could be holding either a full book, or a higher flush, there's very little chance of this.
Pot odds would advise you to fold. Your instinct is right, though, this is not a hand you should back away from. The potential winnings you will get from completing you flush, make up for the difference in the call.
The dealer flips the turn - 4h. You've got your flush but keep your face blank. Big blind calls, the other player calls - you raise to $ 15. As expected, the blind checks but your opponent meets your bet. After the river, the blind folds while your loose opponent checks. You call; your opponent calls and you show your flush - his cards turn out to be Queen-high trips. In the end, you win a hell of a lot more than the original $ 55 that you would have folded on.