Horrible Head's up

[Jerboa]

I've been playing sit n go's on PStars for a short while now, and seem to have the bridesmaid syndrome. 8 tournaments - 6 2nd's, 2 4th.

My heads-up play is just not up to snuff. For instance, tonight: get head's up, I'm in horrible chip position (3800 vs 9700)
We trade blinds for a few hands, trade stealing for a few hands, etc.

I get 55 in the small blind. Raise, he pops me back for half my stack, I re-raise all in.

At the time, it felt like a good aggressive move...but now I'm thinking it was pretty bone-head of me, and that it was a serious mental lapse on my part.

How do you tread the line between aggressive, and suicidal once you get heads-up? Especially when you are the one trailing in chips.

Also, is there any good reading for heads-up situations?