Not just trading but there are a lot of things that we will be failing and that will taught us a lesson.
A lesson that we need in able to make our mistakes correct.
If we will not be making any corrections to our past mistakes, we will never learn, we will be keeping the same strategy or things that we do that would end up to losing again.
The important thing about all this is that at the moment that there is a failure in trading the reason is known, because it is a direct learning, the bad thing is when it fails and you don't understand why ... just like when you win, You must understand why you won, it is the only way to learn from trading.