How do I build a life when I've only focused on my career?

You built exactly the career you planned, and then you looked up and saw you forgot to build a life around it. That is a quiet, sinking realization, and a lot of capable people arrive at it late. You were not lazy or foolish. You poured yourself into one thing so completely that the rest never got its turn. The good news is that it is not too late, even though it feels that way. A life is not built in one grand move. It is built in small, repeated choices, and you can start making different ones now. The same focus that built your career can build friendships, health, a home life, an interest that has nothing to do with work. You already have the discipline. You just aimed all of it in one direction. So pick one thing outside of work that you want more of, and give it a small, regular place in your week. Call the friend. Keep the evening free. Start the thing you keep saying you will start someday. You do not have to change course all at once. You just have to stop pouring everything into the one channel and let a little flow somewhere else.