You should be familiar with the Sandler rule by now that says you must learnt how to fail in order to win. Really this means that you need to be able to fail and accept that failure for what it is, nothing more and nothing less. It is a failure that you should learn from and that should not stop you from making leaps and bounds in the future. Although, for one to be able to move beyond a failure easily and look at it objectively is not often easy for us. We reflect the failure on ourselves as a person for whatever reason. We want to identify with things. We want our identity to be about what we do or what happens to us. This is dangerous for people to do, especially salesman.
When you put so much stock in what happens to you, you are most likely not going to get an accurate description of who you actually are as a person. Or even who you are as a salesman. People identify with what they like to do, who they spend time with, etc. For the most part this is very normal in our society. However, it is dangerous to identify with every single thing that happens to you. You may be a fantastic salesman. But, if you identify yourself with all the failures that ever happen to you, that might ruin how good you are at sales. You must recognize your limits, but also your strengths. Take failures and your shortcomings for what they are and move on. There is no reason that somebody should think that they are worse than they really are. It helps nothing.
Every person should have a sense of self-worth that is not connected to their failures. Most likely one that is not even connected to their job as a salesman at all. You cannot perform your job well unless you have a solid stance of self-worth that will not be affected by something that happens to you at your place of work. You must identify yourself with something bigger than that. Something closer to your character. That is how you will be successful.