A lot of people have trouble grasping the difference between education and experience, or recognizing which tasks and knowledge are within certain areas of expertise and which are not.
Albert Einstein — 'Everybody is a genius. But if you judge a fish by its ability to climb a tree, it will live its whole life believing that it is stupid.'
We are all fish to some degree. The inability of those in our lives to recognize our scope of ability and demand of us accordingly assault our self esteem on a constant basis, and many people are unable to let go when we fail to climb a tree.
Failure is perfectly all right. People who cannot accept failure in others show large predisposition to confirmation bias. They forget that they fail all the time as well, with a personal bias towards their own success only. It also shows an inability to accept that people can grow and change and can learn ; which says more about that particular person's inabilities than your own.
Failure is not something you should fear. Failure is the biggest step towards learning and growing. People who do not fail simply do not learn, and if you meet someone who can honestly say they do not fail constantly then you have met someone who is either oblivious to their own reality or who have been extremely lucky. The latter tend to be unprepared when actual failure finally comes along and their entire life can fall apart over the simplest setback once it inevitably happens.
We should judge people not by success and failure but by how they handle success and failure in themselves and especially in others.