Why do i insta-call, and how do i stop?

[AA Suited]

I've played over 10k SnGs, yet i still sometimes insta-call even when warnings pop in my head.

ie:
$60 SnG, 9 players, blinds 25/50

Relavent stacks:
co: 1600 (Hero = 9 [img]/images/graemlins/heart.gif[/img] 9 [img]/images/graemlins/club.gif[/img])
BB: 1400 (No reads)

preflop:
Hero raises to 150, button calls

Flop (T=375): 4 [img]/images/graemlins/diamond.gif[/img] 7 [img]/images/graemlins/spade.gif[/img] J [img]/images/graemlins/spade.gif[/img]
BB checks, Hero bets 200, BB calls

Turn (T=775): Q [img]/images/graemlins/club.gif[/img]
BB checks, Hero checks

River (T=775): 8 [img]/images/graemlins/diamond.gif[/img]
BB bets 600, Hero insta calls

Thoughts that occured to me just as i push the call button at light speed:
1) He could have a J and the Q was a scare card, thus his turn check
2) He could have 56 and made his straight

With all these redflags, why didnt i stop to think? Why did i insta-call?

And how do i stop?!