Are you too cautious? NO! By riding defensively (or even just not agressively!), you'll live a lot longer. Too many psych(o)lists think that just because a car (or truck) driver will generally be held to be at fault when they get smacked off they won't be hurt - dead is however dead.
As a long term biker (motor as well as pedal), I've never been involved in any vehicle - vehicle contact incident. I've come way too close for comfort a few times but expecting every Joe C*** to pull out on me has meant that I've had the levers/pedals covered and ready to stop/swerve. Most recently, a driver looked me straight in the eyes then pulled across in front of me as I was going straight over a set of (green) traffic lights. I had my headlight on (generally don't, having had some tw@ tell me he thought I was flashing him across...) as well as right of way. His children may have learned a few new words - spoken in a normal tone through his open window ("There's no need for that language!" "Well, there was no need for you to try to f****** kill me!")