The way of least resistance would be to go with the argument that only children can change their personality. That’s the easy excuse for being immature. To hide behind the lie that my personality was irrevocably casted in the current form through my upbringing, cannot be true.
Every little baby born into this world starts off with potential. Whether that potential will develop to its full capacity, will depend on all the influences, their education, culture and ultimately their choices. Although negative influences could hamper the ease with which choices are made later in life, it cannot be the ultimate excuse for being a failure. It would be an absolute waste if you end up further back than you have started!
It is never too late to regenerate your growth to maturity. This is done by consciously considering the level of your achieved capacity. Actually an easy question: “Am I the person I know I can be?”