worst brain freeze ever???

[bocablkr]

I need to vent - what an idiot I was last night. Playing $20 no-limit holdem tournament with 746 players. Two tables left with 10 players - need to get down to 9. I am in 6th place with $75,000. Chip leaders have around 200,000. Blinds are 4000/8000. All I need to do is wait out one player. I get AJ unsuited and raise all-in to steal the blind out of position with a chip leader ahead of me. WHY??? He calls with AK. What was I thinking - I have no idea why I did something that stupid. I had been stealing blinds before this but should not have been doing it at this point. Has anyone else done anything this stupid???