Self-direction — agency over your work and your circumstances — is the key to life satisfaction. Make sure you grant sufficient self-direction to the people around you, and make sure your career choices result in greater agency for yourself.
If you can help it, do not partner with anyone. The more partners you have, the more you have to split the pie. The more partners you have, the more you have to fight for your point of view. The more partners you have, the more time it will take to execute anything. Co-founding is overrated.