I have never understood why some people seem to be natural string breakers. I have played very strongly in very loud environments and I use a heavy pick but rarley snap a string and yet I know people who play lightly and use a light pick who are constanly breaking strings for no apparrent reason.

Having said that, if you are consistenly snapping the same string in the same place, have a look at your instrument and take note of where it is failing. I have know a small chip in a bridge, a bad nut and bad tuning pegs cause these failures.

Jon