That is true. I have a mental game I play on myself when I don't want to work out, even if I am legitimately tired etc. I tell myself to just start and go for 5 minutes, and if I feel like quitting after that I can. I quit exactly one time, and that was years ago, and I was so exhausted my HR would not rise up despite working hard, and I HAVE NEVER REGRETTED a single workout. I am always glad I went ahead and did it, and often add even more time on than I original intended (from 45 min to 60 etc.)