Opinion of others about you is important. But more critical than that and what matters most is - your self-opinion.
If you believe you are weak, if you believe you are sad or that you are an eternal loser ... can your projections of behaviour be any different than that ? Do not over value what you are not. The world is full of boasters. But certainly do not undervalue what you are, as well. That is important.
The greatest blunder people make is to pass-on the remote control of their assessment & thus their happiness, on to others. All that you need to really focus on is what brings you alive.
Low self- worth is literally like driving your car on the free-way of your life literally with your hand-brakes on. You can never win such a race.That apart. You will also damage your car and will never be happy. Those are collateral damages.
Rightly said Edmund Hillary. It is not the mountain we conquer but ourselves! You have to conquer the mountains of your choice. But first, begin with yourself!
So next time your boss tells you - "You are stupid" ..... well tell him with your full Confidence - you are not !