There are no mistakes, there is only learning

If you are not making mistakes, you are not doing anything new,
If you are not doing anything new, you are not learning
If you are not learning, you are not progressing
If you are not progressing you are ready to die.

To explain this: if you are not making mistakes you already know how to do it right, thus it's nothing new, and by doing it over and over again you are just passing time, waiting something to change and the only thing that will bring change by doing the same thing is ultimately death.

Challenges bring growth. If there's no challenge, you've reached your peak. Once you can do something effortlessly then you have mastered a skill, you have found yourself in it. The effortlessness of it directly indicates your oneness with it. If it takes effort then there's still more to learn, you are not yet one with it. But if you see people making mistakes and failing, then you see people trying something new, moving out of their comfort zone and challenging themselves, growing.

Only stagnating people do things that they've already mastered.

PS. A synonym for a level of effortlessness is efficiency.