I think about lots of things at 45km/hr, mostly "I hope I don't get a flat on these [censored] tyres" because the only time I'd be doing 45km/hr on a bicycle is down a hill..
It may just be a personal habit from judo training when young, where you were taught to roll to land on your shoulder blades. So much gentler than driving knees and palms into the gravel. Ouchies.