A painful lesson about growing up:
Every few years, the game you're playing in life changes ― and so do the rules.
A lot of people fail to make this mental switch and keep stumbling in life.
Some examples:

High School:
The game is popularity and it pays to be arrogant and cliquey.
But when you go into the workforce the game is cooperation ― being snobbish and cliquey will rub people the wrong way and undermine your career.

College:
The game is compliance. Follow the rules, show up to class, memorize the books, and you're guaranteed success.
But adulthood doesn't come with a textbook of clear instructions ― if you can't cope with ambiguity, you're toast.

Work:
When you're working alone, the game is maximizing your productivity.
But when you're a manager, the game is maximizing your team's productivity.
Most managers, especially at the start, fail to adapt to the new rules and settle into mediocrity.

About every 5 years, you'll be switching into a new game. Your instinct will always be to keep doing what you're doing.
But the reality is that every 5 years you need to unlearn a lot of the old habits that served you well, and start building new ones from scratch.