Not all workouts will be the best. Sometimes, the goal needs to be to finish. It might be ugly, sore, tired, or broken. Finish anyway.
This applies in other areas, too. When you're implementing a new diet, not all days will be pretty. You will struggle on certain days. You'll fall off track from time to time. It's not going to be perfect. Keep going anyway.
The line and commitment need to be 100% defined. That doesn't mean you'll hit it perfectly. It just sets the bar for knowing if you cross it. That's not time to panic. It's just time to accept the fail and to get back on track immediately.
No excuses!