Too late!

I don't wear a helmet, not because they're uncool but because they're unnecessary. Yes, I've heard all the stories of "if I hadn't been wearing my helmet I'd be dead" - they're sincere, but mostly mistaken. Ordinary cycling helmets aren't rated to give protection against the impacts that are REALLY going to crack your skull - they'll save you cuts and bruises, but rarely brain damage. Cycling is pretty safe and helmets haven't made it safer. As helmet use has increased, the already small incidence of severe head injury to cyclists has not declined. So they are, in my opinion, pretty much a waste of time.

Were I a downhill MTBer, I'd wear one, but it would be a full face helmet that gave meaningful protection. On the roads, I can cycle well enough that the only thing likely to do me serious damage is being hit by a motor vehicle with an inattentive driver. In that event it is unlikely that a helmet would give me much protection. No helmet.