You are not just a flame, you are the fire.
You are not a small puddle, you are the big pond.
You are not the darkness, you are the light.
You are not what others think you are, you are what you think you are. You are what you mould yourself into.
Opinions differ from person to person. Your own opinion about yourself is something that matters. Sometimes we tend to think that others are right and suppress our own opinion. We are humans and knowingly or unknowingly we end up judging someone. We pass out compliments and our opinions to others. It's in our nature. It's just that some people do it in limit and some make it as their regular duty.
We receive both positive and negative feedback from others. We must try and learn to embrace positive feedback and ignore the negative ones. It's not easy to let go of negativity because these things stick in our mind and compels us to question our own self worth. They may be right or wrong, but that shouldn't affect us. For example, if someone says you are weak, but deep down you believe that you are much more stronger, then that opinion can't break you.
Similarly, if someone says you will be a great person in the future, but all you think about is your flaws, mistakes and weaknesses, then even that positive opinion can't bring any difference in your life unless you think positively about yourself. Our own attitude and perspectives about ourselves is what actually matters.