I find it interesting how out mental state influences performance. As I mentioned in another thread, I ride a certain hilly route semi-frequently (because my area is plagued by hills, if you want to get anywhere) and there are a couple of double digit climbs that kick my behind. One day I introduced a more powerful friend to ride with me on that route, and I was amazed at how much better/faster I did the same climbs without feeling nearly as whipped at the crests. I am sure if I rode that alone, I would have suffered like usual.

I usually gauge my fitness by my power numbers and how I did on past segments. One thing I need to be mindful of is not pushing myself to the limit too often because of what I have read about those king of efforts leading to the calcification of arteries.