Anything and everything. What i know is if I'm thinking about how far it is to the next control and what the time is like I need to think of something else. I've been known to sing on rides, talk to animals, signposts (and even people!). Other thoughts include Looking at the scenery, telling my legs to stop moaning, explaining to the Police officers at 5am that "I haven't crashed and I intended to lie down here for a while", "er no I'm not drunk", "yes it is a long way", "I don't know either!" ...