Interesting, James that it has had the effect of slowing you down a bit. We all (especially men) think we're invincible/immortal, but I'm afraid none of us is. It's no bad thing to take it a bit easier. But again, my advice would be not to stop driving. We all have to take some risks just to live.
I rode a motorbike for a few years and the thought process is quite enlightening - you are at a far greater risk, but I enjoyed the speed/acceleration.
But things in your life change, I'm now married and hope to be a father during 2008, all being well. I'm not inclined to go out on the bike at all at the moment, as you're at the mercy of so many things beyond your control, and a) you are less stable on 2 wheels and b) if it all goes wrong, you haven't got a ton of steel, crumple zones, seat belts, airbags etc to protect you.
Best advice at my m/c club (when considering whether to make an overtake or not) was "might you meet yourself coming the other way?" - i.e. although the manouvre would be safe if everyone else is doing 50mph and keeping to their own side of the road, what if there's another bike (or Ferrari) coming the other way who also decides to overtake at 100!