I often have that problem. I put goals for myself, and I'll be pissed if I'm off. A couple days ago was only my third ride (3 days in a row) after a 2 week break from surgury recovery. I had a somewhat newer bike than before...and on this 8-10 mile stretch I remember the last time I did it before the surgury I averaged 17-18mph. On that ride a couple days ago I found I averaged 16mph. 16mph on a newer bike, not a good one, but better than what I had (I bought it for 50 bucks). When I was riding, it felt like I was in just as good shape as I was 2 weeks ago. So I was in a bad mood, I didn't even ride the next day because of it. I felt just like Turantula did. Maybe I woulda rode yesturday, but my neck felt a bit sore (surgury recovery).