Folding my top set at turn... Stupid?

First of all , hi =) My first post although i have been watching the forum for long time.

$400 NL , 5 players max

Seat 1: Hero [J[img]/images/graemlins/diamond.gif[/img],J[img]/images/graemlins/club.gif[/img]] ($558.40 in chips)
Seat 3: SB ($$398.95 in chips)
Seat 4: BB ($238.95 in chips)
Seat 7: UTG ($107.10 in chips)
Seat 8: MP ($226.45 in chips)

ANTES/BLINDS
SB posts blind ($2), BB posts blind ($4).

PRE-FLOP
UTG folds, MP calls $4, Hero bets $16, SB calls $14, BB folds, MP calls $16.


FLOP [board cards 7[img]/images/graemlins/club.gif[/img],4[img]/images/graemlins/spade.gif[/img],J[img]/images/graemlins/heart.gif[/img] ] (Pot $48)
SB checks, MP bets $10, Hero calls $10, SB calls $10.

TURN [board cards 7[img]/images/graemlins/club.gif[/img],4[img]/images/graemlins/spade.gif[/img],J[img]/images/graemlins/heart.gif[/img],8[img]/images/graemlins/heart.gif[/img] ] (Pot $78)
SB checks, MP bets $30, Hero bets $150, SB bets $378.95 and is all-in, MP folds, Hero folds.

It's one of the few times i slow play a set like that. I wanted to give a chance to the MP to catch his Ace because i am sure he had that J but the other one i was guessing he was either on the straight draw or flopped two pair..i feel kinda stupid folding on turn. I am looking forward at your thoughts and thanks for any replies!

/Edit: No reads at the SB. He has only been in the game for a 2 hands.