Criticisms

"Criticism may not be agreeable, but it is necessary. It fulfils the same function as pain in the human body. It calls attention to an unhealthy state of things." Winston Churchill

They are a necessary evil because we are terrible judges of ourselves. Heavily prejudiced, we will offer excuses (that we would withhold others to use) if they are to cover up our own mistakes. Why? Illusory superiority: a cognitive bias whereby we overestimate our own abilities. 

When a sample group (admittedly of only 161 people) was asked whether they believed they were above  or below average drivers, 93% of them placed themselves in the top 50%. Of course, while it could be within the realms of possibility that all 150 of those who proclaimed that they were better than average, were in fact better than average, it is an unlikely prospect. What's more likely to be at play? Man's ego.

And it is criticism that restrains an ego. Ergo we need it. 

So linger not on the throbbing pain of rejection or the stinging blow of words best left unsaid, nor be distressed by the disapproval of somebody you hold dear or what was said merely to upset. Instead, recognise the unhealthy state of things within yourself. (At the very least, that you gave credence to those who would act more as conspirators plotting your downfall, than critics offering constructive advice.)

Then fix it, and watch those who would see you fail gnash their teeth in despair.