See being positive is the reason that you should be self motivated. Now as you are between a lot of negative people then you will always get the negative comments. Now in such situations you have to make your mind in such a way that all this negative words get reflected back. You should stay calm and don't mind with the words. Keep on practicing. Don't see videos or anything to motivate yourself. Practice self motivation. Slowly you will gain the positive vibes.

You may feel like it is a abstract answer but implement it. You would see the improvements.

I hope my answer helps. All the very best for your future endeavors!