Have you considered getting one? It can be very useful to work out what is going on. Often it is just a lack of confidence creeps in when you are on the right track and you start to second guess where you are. Changing tactics during a leg is rarely a good idea.
O-ing thanks for the advice. I think it may be more to do with having a few beers the night before. My head wasn't into it. Also my eyes are starting to get worse. May need glasses.