It is perfectly normal to take negative comments about us to heart; however, by doing so, we only hurt ourselves and lower our happiness levels. Do not focus on the things you cannot control; instead, focus on what you can control and aim to better yourself.
Understand that while you cannot control what people say about you, you can control how you react to it.
You can get upset and begin to shy away from others for fear of being judged, or you can ignore the nasty comments and stay confident in doing what you know is right. Recognize that someone will always have something unpleasant to say, so you might as well continue doing the best you can.
Regardless, do try to better yourself.
Keep a record of the mistakes you have made, and fairly judge and criticize yourself. Also, ask people for unbiased, constructive criticism so that you can identify the areas of yourself you need to improve on.