According to Osho, your immaturity persists because you still obey the inner voices of parents, teachers, and leaders; true maturity requires killing these internal authorities, and even the old self, so you can decide for yourself. A mature person stands alone, lives by inner understanding, seeks no approval, and never trades freedom for respectability, whatever the cost.
To grow up, stop letting the voices of mom, dad, and teachers run your head; choose for yourself with courage and freedom.