I met my H when we were at school.
We married at ages 22 and 21, married for 60 years.
He had dementia for several years and I cared for him until 4 months before he died, I was too worn out to carry on though I may have done if I had known how little time was left.
You do carry on because you have only one alternative and that is unthinkable to most.
Mt theory, on seeing friends like myself is that the older you are, the better you cope, you have come to the realisation that it will happen one day and awful as it is you have been subconsciously preparing for it.
My H died 3 years ago last Monday, my consolation was that he didn’t live through Covid lockdown.
That would have been unbearable.