The wake of aging parents transitioning (death, stroke/care home) has without doubt accelerated my mental age, which in turn has changed what I'd call my horizon. When younger and prior to said events, the horizon was far away; time enough for everything/anything. Not so much anymore, much greater sense of uncertainty.
I felt like a 20-something until my late 30s when I had children. When my third kid came, I felt like I skipped my 30s and turned 40... right before my 40th birthday.
Midlife crisis definitely happened for me, and might actually have been my internal age adjusting to my external one.
Makes me wonder if I'll feel 47 for the rest of my life...
Mentally, I felt older, "an old soul". But physically, not having the energy to do anything, sleeping almost in excess, not going outside, not laughing or smiling . . . they all seem to have kept my body younger.