I do and its usually related to how I feel before the ride physically. If I stay up partying all night I'm more nevervous on the bike, make more mistakes which leads to being more nervous etc.

Now...there's another voice I hear that says "go gettem" and "you can go faster than this". Its very infrequent but it does sorta get me in the zone but the loudest it every screamed was right before I tossed my bike at the Gap.

I guess the secret is to listen to both but don't let them control you. You don't want to be too scared or too confident because both are keeping you from concentrating on riding correctly.