The trick to bluffing don't bluff weaker players you might be able to get a good player to fold a J10 on a jack high board if the bets are sized right but even then beware most people won't give you credit if you've been overly aggressive and running over the table previously.
that J high board to a weaker player he's all in with J5 even if you have a good semi-bluff opportunity
I think lots of bad calls are made when people take a stand to a good player frustration sets in, after all, if you've been pushing these guys around now they're getting pissed.
it's a tough call most CB's are bluffs if table image is taken into account and you've played an aggressive game eventually you'll get called down lighter it's setting your self up for a big pay off but also setting your self up to fail at a big bluff.
play small ball, steal/bluff lots of little-uncontested pots or when you have a good stack to outplay a little.
towards the end of a tournament, you have to bluff/semi-bluff to win if you play fit or fold poker you'll get eaten by the blinds.
if you don't bluff and just play solid cards anyone paying attention will fold to your raises you'll define your range so well that when the big stack decides to call your raise with 78s and you miss he's outplaying you.
it's all a fine line and a world of contradictions that comes down to, timing
tells, table image, bet sizing, M-zone, player types etc
As for bluffing when you know you shouldn't, it can be a fine line between winning and losing just try not to get your whole stack in on a big bluff