God I Really Friggin Hate Flopping Sets

[private joker]

Party Poker 0.5/1 Hold'em (9 handed) converter

Preflop: Hero is BB with 5[img]/images/graemlins/heart.gif[/img], 5[img]/images/graemlins/diamond.gif[/img].
UTG folds, <font color="#CC3333">UTG+1 raises</font>, MP1 calls, MP2 folds, MP3 folds, CO folds, Button folds, SB calls, Hero calls.

Flop: (8 SB) 9[img]/images/graemlins/club.gif[/img], 5[img]/images/graemlins/club.gif[/img], J[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(4 players)</font>
SB checks, <font color="#CC3333">Hero bets</font>, UTG+1 folds, MP1 calls, SB calls.

Turn: (5.50 BB) 8[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(3 players)</font>
SB checks, <font color="#CC3333">Hero bets</font>, <font color="#CC3333">MP1 raises</font>, SB folds, <font color="#CC3333">Hero 3-bets</font>, <font color="#CC3333">MP1 caps</font>, Hero calls.

River: (13.50 BB) 4[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>
Hero checks, <font color="#CC3333">MP1 bets</font>, Hero calls.

Final Pot: 15.50 BB

This has been happening so often that I called out QT on the turn. Why did I call the turn cap and the river bet?