For me, the flying objects are usually bugs, when I'm out cycling. More than once I've had yellow jackets bounce off my glasses. :O

Late last summer, I took a ride one evening when, in any wooded area, the air was absolutely thick with gnats. I wound up tying a extra bandana over my mouth (flying protein supplements do NOT taste good!) and adjusting the one around my forehead to close the gap over my glasses for good measure.

The trick is to have multiple pairs, to the point where you find them at the same rate you lose them.