Going to the gym when you REALLY don't want to go to the gym
It continues to amaze me what a disconnect there is between what your mind thinks that you can do and what you actually can do.
I had a stressful couple of days and I also didn't eat as much as I normally do. I also hadn't had much sleep. Yesterday the whole day I was just beat and thought several times "How in the hell am I going to go to the gym tonight?" To top it off I wasn't able to get to the gym until around 1am, which is late even for me. As I was walking up to the door I thought "WTF am I doing here? There's no way I can get a good workout in this condition."
I then went inside and proceeded to have an amazing workout. I actually did better with dumbbell benching than I've ever done since I started training. I felt strong and energized the whole time. If I would have actually acted on what I was thinking before I hit the gym I would have missed out and would have been none the wiser.