Is there a limit towards any challenge you faced? How would you define it as a real challenge?

Yes, it is hard to set a certain threshold and follow the routine you planned repetitively, but without it the bar height will fall lower and lower and gradually follows the way you planned it, no expectation at all. While on the other hand, having a strict routine causes you to lose your enthusiasm as you're bounded by the rules you set, you feel challenged, limited by protocols and in repeating manner for each and every cycles before starting to get bored.

How to balance it? You define it.