I suck

Sorry maybe i'll just get flamed now for asking basic questions or whatever, but i am pretty frustrated now so...
I am usually playing 11$ and 22$ sng's at party. my game during the first levels and fases is working ok. My problem is that I really seem to SUCK during the bubble.
I am very stable at around 36% ITM but got a negative ROI as I usually end 3rd when I get ITM and
a very high % of 4th places. I seem to never get it right.. i play too agressive or to passive. I am very often chipleader when its 4 or 5 people
left and then I mess everything up. you guys that master the bubble play, would be grateful for any
advice or links to usefull information about the subject. The search function doesnt seem too good?