I have a few.

Mental. I never feel I will ever be good enough to win anything. I continue to think that there is and will always be someone better than me out there racing that day.
I continue to tell myslef to do as good as I possibly can. Don't go out there and feel defeated before the race even starts. Enjoy the day and thank God I have the ability to do what I want to do.

My physical structure:
I have a twisted pelvis. My right foot is positioned forward and to the right way more than my left. It makes for lopsided pedalling and loss of power. I have been fitted several times and each time I come out a little better but not good.
I left it up to myself. I have purchased wedges that seem to have helped a great deal. I also tweak my cleats small bits at a time. Slowly it's coming around, but I will have to start over when Santa brings me the Fuji SL1.