There always will be someone who doesn't believe in you and your ideas. Don’t even think about them. Just invest your time and thought in your dream, and you will gain something unchangeable.
Don’t believe them.
The real world is full of pessimists who will try to put you down by convincing you that you will lose and waste your time in vain.
Don’t make their reality yours.
They will convince you that your ideas are impossible, because they expect that every new idea will fail.
Don’t make their words a justification for not trying.
They are sure that society isn’t ready for changes, but you shouldn’t give up without a single try.