Last night I saw the flop with two others.
I had a nut flush draw and I read that my opponents had decent hands.
I was out of position and checked every street including my 5th diamond on the river.

I called each of the two bets prior to the river. The bet on the flop was one third the pot size (justifiable call). The bet on the turn was the size of the pot - here's my justification: I knew these guys were going to keep pushing their chips into the middle. To call the turn bet, I would have had to call $5. The pot at the end of the hand turned out to be $35. 5/35=14%. Odds of me hitting the diamond on the river = 18%.

Justified?