It is not about motivation, it is about dedication.
There is power in the practice of regularly doing reps in workouts. I always had the mentality of “one and done” when I exercised. Now as I think about it, that is just silly. Doing a hard routine is supposed to be difficult that is why you should do it again during the same workout. You can only get stronger if you know your limits and push them. Also as I mature my exercises I do multiple reps throughout the day to push the limits again. If you can do 5 push ups in the morning you can certainly do 5 push ups at night. You’re only going to get stronger.