You have become the means to your goals' end so much that you have no idea who you even are anymore.
There's no "you" left because you neglected it out of existence.
Every thought, action and desire was channeled towards achieving the goal.
It's the classic post-success identity collapse.
You didn’t just achieve a goal, you became the goal.
Advice such as "try things out" won't work in the beginning.
The person genuinely has to go through a similar process as the one after a really abusive relationship and rebuild their internal being from almost scratch.