Of course cycling isnt as safe as getting around in a 2 tonne vehicle designed to be crashed, tested to destruction. It is still safer than most people assume, especially if you take it seriously and dont take risks, when you eat into the margin of safety is when you have problems.
I see it like this, I need some exercise, I am too lazy and get too bored spinning in a leisure centre so I ride on the road, that exercise is getting me fitter, potentially it may keep my cardivascular system in better condition so may well be safer than sitting on my arse in the car.
I try to assume everyone is an arse and out to get me, that every parked car, junction, driveway has a car or somethign ready to jump out, every ped is going to walk into the road, make any assumptions the other way and you are in for a painful dissapointment, I try to learn every possibility.
I love my mirror, I struggle without it, I still look round but this means I can see behind me every couple of seconds to see what motorised aggro is about to appear, I had a helmet one, that did wobble, I got a Cateye bar end one, looks a bit gimpy but I would hate to be without it.