Playing pattern Question?

[Fitz]

I've been tracking my results closely over the last year or so, and I've discovered many interesting things. More than 70% of my sessions are winning sessions, and I average a little over 1 BB an hour. This is all great, but I often seem lose early in session. I'll often dig myself into a 12 to 20 BB hole. Most of the time, I'm able to get back to even and then some, but it is a pain when it happens like that. I'm guessing this happens 20+% of sessions. I just wonder if this happens to anyone else regularly, and what might be a cause.

Thanks,