I have a really hard time keeping up with HIIT workouts. Part of the problem is that I'm not super strong, but I also think on some level I don't like them. I've started doing the low impact versions of HIIT and that has helped, plus I am taking Zumba 1-2x per week for cardio.
If you enjoy HIIT, why? What is going through your mind during the hardest parts? I am finding that my thought process is largely negative, but I wonder if I could retrain my brain to think positively about the experience.