It doesn’t sound too far off from my experience of depression. When I was in my 20’s I fully expected to be dead (one way or another) before 30 and I felt pretty blasé about it. Having 50+ more years of misery seemed intolerable by comparison. Then 30 kinda snuck up on me and things really had gotten a little bit better, so I just kept on going just to see what would happen, and have kept keeping on ever since.