That's funny.. I'm just the opposite - I have a hard time staying with a set plan. I'm always changing something.. taking an extra rest day, working out a day early, splitting my workout into 2 or 3 short ones, trying some crazy exercise I read about on the board, maxing out when I'm not supposed to, going light when I'm not supposed to, etc.
I've been doing well with a WSB style workout because it allows a lot of flexibility.