2. If you do, tie the hat on firmly first.
3. If you ignore rules 1 & 2, avoid cycling down hills.
4. If you ignore rules 1, 2 & 3, and you go down a hill fast, and the hat starts coming off, ignore it. Under no circumstances give in to either of the contradictory urges to a) grab the hat, b) hit the brakes.
5. Otherwise you will plough the bike and yourself smack into the tarmac, knees first, knock the wind out of yourself, and knock your front wheel out of alignment, such that you have to pay the bike shop a tenner to realign it. And end up with bruises like these:
Yep, that was the famous "Fell off my bike whilst on a cycling holiday incident". That it was my own fault, and that I fell off because I'd gone to view a church, just added insult to injury.