If - say - it's winter, and your brother has left his mountain bike in the garage while he is at university, and - say - you borrow it because it has big grippy tyres and your bike has 25c road tyres on - you will still fall off it if you turn right into your own road across a frozen puddle. This would undoubtedly be made more certain if you were trying to skid it in the loose gravel (we had rubbish roads even then), but the effects would be lessened if you were returning from the pub.
Your brother will probably notice the scratches on the paint.
Other things.
If you attach something to your bike or rack and think 'that looks a bit dodgy but it will stay on, I'm not going far', it will fall off.
75% of motorists would rather get to stop in a queue at the traffic lights a few seconds sooner rather than allow you enough room
If you notice a nut being loose, it will fall off before you get home.
Don't go to the front of a queue at traffic lights unless there is an advanced stop line. The front driver will invariably not see you and try and cut across you. Go between the first and second vehicle (assuming the second vehicle isn't a lorry, as the driver won't see you at all)
On that note - lorries have larger blindspots than you can imagine. It's best to assume the driver cannot see you, and will never see you, and act accordingly. In a fight between a 10 tonne lorry and you on a bike, there is one winner regardless of who is obeying the Highway Code.
Pedestrians think shared use bicycle/pedestrian lanes are funny coloured pavements and will wander all over them. If it is marked out as bikes one side and pedestrians the other, more than half the pedestrians will be on the bike side.
Taxi drivers don't care about anyone else
