If you want to learn from your mistakes you have to first admit you made a mistake. If all you do is place blame for it on someone else then you will not learn what you needed from it. We all make mistakes. In fact many things that we consider necessities today would not exist if those responsible for it didn't learn from their mistakes along the way and made adjustments. Like the old saying goes "If at first you don't succeed, try and try again". So if you don't admit when you make a mistake you won't adjust to be able to succeed.