I think for me it was 39. I had lost my girlfriend and my job; I had quarrelled with, and thrown out, my room-mate; there was a serious recession here in Canada (1991), and I was spiraling deeper into debt every week.

Happy frickin' Birthday, indeed. I went into therapy, but it took a while to climb out of that hole.

40 was 'same old, same old'.

Even 50 was marked more by friends and colleagues than myself.

I think it comes down to what's happening in your life at the time. The calendar has bugger-all to do with it. I turn 54 this fall, and by then I hope to be embarqued on a new career in a different line of work. External change happens regardless of what you do, or don't do, inside. If the person you are at the time is ill-suited to your circumstances, you will have to make some changes, else some changes will be imposed on you by your surroundings.

Its up to you.

Either way you get older, or you die.