Do nothing that doesn't support your rush. If you are the kind of person who thinks drugs are good, but medication is bad, you must make exercise your drugs, not your medication. Let nothing stop you. Let your inner Sick Jock drive you to sit-ups on the cold tile floor of a hotel bathroom. To swim at dawn.
Exercise turns out to be a mental challenge more than a physical one.
It is all about what you have decided you can do. The muscle you stretch most thoroughly is your will, and just as the physical fitness you get spills over into other areas of life, so will the tough-mindedness. The finish line is in your head. Even your thighs are in your head. If you have a will of steel, you can have abs of steel.