The short answer
You did not lose yourself — you just had your whole self stored in one place. Retiring young means you have real time to find out who you are when no one is watching the scoreboard. That is not a crisis. It is rare and worth using.
You have spent years being defined by what you do. Research on identity and work shows this is common — we fuse our sense of self with our role, so when the role goes, the self feels hollow. That hollowness is real. It is grief, not failure. You are mourning something that genuinely mattered.
Here is the reframe Marcus Aurelius quietly offers: most people who started when you did are already gone. You are still here, and you have open time ahead. The identity you carried was never the whole of you — it was the container you lived in. Containers can change. The person filling it does not disappear when the container is set down.
This week, write down three things you did inside your old identity that you actually loved — not the title, the feeling. Then write three things you were curious about but never had time for. That list is not a career plan. It is the first honest look at who you are when no one is grading you. Start there.