Who has a short window to capture the momentum required to head out for a hard workout? I planned my morning around heading out for tempo intervals at the track. I got waylaid on the way back from coffee. Now the excitement has diminished. I'm heading out now, but $10 says I get to the track, run a few laps hard, and end up going for a mid-distance run to fill up the time.
Once when I tried to become a golfer (don't say it) I had a great drive, or a great chip, or a great putt, or something -- and I complained to my playing partner, who was a golfer, that "I'd be good if I could just be consistent." He responded, "no, you are not consistent because you are not good."
Difference between being a professional and being a weekend warrior: the ability to get in the right frame of mind at will rather than hoping that the frame of mind occurs on its own with sufficient frequency actually to get something done. This most definitely extends to writing as well.