I always remember what I learned in driver's ed about how safe a driver you are. Not having had an accident isn't the indicator, but not having near misses/barely avoided accidents is. If you have ever had to slam on the brakes, swerve to avoid something, or take evasive action of any kind, you could be driving more safely - driving slower, leaving more distance between you and the car ahead, paying more attention to your surroundings etc.
I look at computer security the same way, the safety of your system should not be measured by when you had your last infection, but the last time something tried to get IN and was caught. If you're constantly getting attacked by virii and malware, you probably have to think about what you're doing to expose yourself to such things. Unsafe browsing, torrenting, downloads from questionable sites, angering
@Umbra etc.