Individual effort is like climbing a ladder, but working at a rapidly growing company puts that ladder on an escalator. The company's momentum creates opportunities and upward movement for you that are independent of your own climbing speed, drastically accelerating your career progression.
Reaching a long-sought-after career milestone, like a specific promotion, can unexpectedly lead to depression and a sense of aimlessness. The "chase" provides direction, and without a new goal to replace it, you can feel lost, like a dog that has finally caught the car it was chasing.
A critical career inflection point is moving from solely executing tasks (writing code) to influencing strategic decisions about what problems to solve. True value and impact come from being in the room where decisions are made, not just being the person who implements them.
Instead of striving to be the best in a single domain, find a unique intersection of skills you're good at. Being able to negotiate across both design and engineering, for example, creates a niche where you are the "only" person with that combination, making you more valuable than being just another "good" specialist.
While some aspects of life can handle stress and bounce back ("bend the reed"), others, like key personal relationships, can break permanently under extreme pressure from overwork. The small gains from achieving a career goal a few years earlier are often not worth the risk of irreparable damage to your personal life.