It's okay to admit your defeat. It's okay to lessen your dreams. Be more realistic. Those all are the part of maturity.
But... Don't give up on it!
If it is something important, then don't ever lose it!
Because dream is the part of yourself. It is a depiction of who you are.
Without 'it', who do you think you are?
Don't ever lose dreams. Because without your dreams, you're no other than an empty shell.