The thing you sell most in this life is yourself. Believe in the product.
No one can do it for you. People will support you, encourage you, push you, and remind you of things you have forgotten about yourself. Then they will doubt you, criticize you, hold you back, and warn you to be careful.
External validation—while sometimes helpful—is unreliable and unpredictable. Will people love your idea or hate it? Is your personal growth goal met with enthusiasm or sarcasm? Do people think you are good enough to do the job or do they question your ability?
External skepticism, for so many people, triggers internal doubt. When your self belief is weak, you are easily influenced by outside opinion. You look for approval on the outside to overcome your hesitation on the inside.
Turn that relationship around. Give yourself internal validation to overcome external hesitation.
The first person you need to sell is yourself. The person who most needs to believe in you is you. The world already questions your ability. People already criticize you. Even your family doubts you. No one is free from this burden. We all experience it.
Choose to believe in yourself. Strengthen your resolve to understand who you are, what you are capable of doing, and why it matters. Strength requires work. Work requires practice. Practice takes time. Do the work.
Do not ask or expect anyone to do it for you. It is not their responsibility. It is yours.