Part: Part Five - Betting Before the Flop

When your bluff gets four-bet

Pre-flop
Blinds 100 / 200Pot 7,300 (36.5 BB)BBA♠5♠● 25,000 (125 BB)YOUyou 3-bet to 1,800 as a bluffBTN● 25,000 (125 BB)Button4-bets 5,200 (26 BB)SBfoldsD

You light three-bet a button steal to 1,800 with A♠5♠ as a bluff - and he four-bets to 5,200.

Your light three-bet got four-bet. With A♠5♠, best?

WhyFold. Your three-bet was a bluff for fold equity; the four-bet means it failed, and you're now against a value-heavy range A-5 can't profitably continue against out of position. Give it up - don't pour more chips in behind a busted bluff. (A five-bet bluff exists against the right opponent, but folding is standard.)
What happensYou fold.  The bluff didn't get through - you give it up cheaply.
A light three-bet is a bluff, and when it gets four-bet the bluff simply failed - you fold rather than compound the mistake. Knowing when to give up an aggressive line keeps the cost small.

When a light three-bet gets four-bet, usually fold - the bluff failed, and reloading behind it out of position just throws good chips after bad.