To quote Edison, “I have not failed. I've just found 10,000 ways that won't work.”
Failure is the best teacher because it forces you to actually test your assumptions to figure out why something didn't work. Humans have a tendency to be uncritical of success; why do I need to think more about that, I've already figured it out? However with failure we can't proceed until we have reevaluated the problem to find another potential solution.
If you aren't failing, you aren't challenging yourself enough.
I agree! I assume its kind of natural to "not break it if its already working". Thankfully we have failure to keep our asses in line haha.