You could define the way you feel about yourself by someone else's opinion of you - but why would you?
When we feel personally attacked in life we have a tendency to forget about human tendencies.
Often times people are reacting to us out of emotion that isn't fully attributed to us.
Little pieces of bad days, past hurts, assumptions, and defenses work their way into every situation and are then projected onto current realities.
Because of this we are often attributed qualities or failures that aren't really our own.
If we change how we feel about ourselves based on every last person's momentary judgments, we are doing ourselves, our esteem, and our self identity a great injustice.
Only you know who you are and what your intentions are.
There are times that you do something forseeing one outcome and getting a completely different one. Other times we completely overlook at potential negative side effect. That is the course of life. Things don't always go as expected.
Go into each thing you do with the best of intention. Be willing to admit when you are wrong or when something goes completely differently then you expected, but don't call everything failure or define yourself about how people feel about you in any one given situation.
And most importantly don't go chasing your self worth around based on what other people think of you. If you do you'll be chasing it around for the rest of you life and constantly neglecting the one person that knows the truth about who you are - YOU.
Do your best. Operate with the best of intention. Be open to explaining yourself when needed. But never let anyone tell you who you are, what you are capable of, or to define your motivation.