2 things factor greatly with me as far as breaking strings go;
1) If my picks are getting worn down and have snags in them, the pick will catch on the string, thus eventually causing the string(s) to break before their time. Keep a close eye on your picks. Toss them when they start to show signs of wear.
2) If I am playing in a humid environment my strings have a tendency to break much more often than playing in a non-humid or climate controlled enviroment. Keep your strings wiped down as often as you can and place your instrument in it's case (closed) while on break.
I wouldn't be too upset that you're not breaking strings while playing. Most of the time when one breaks a string one's instrument goes awfully out of tune.(mine do at least) Some people, like Stevie Ray Vaughan, can break a string and make it look cool. SRV used such thick strings that when one broke the rest were tight enough to prevent his guitar from sounding so out of tune. Most people lack the prowess SRV had and most peoples instrument's sound like poo-poo when a string goes pop-pop.......
Give everything but up.