When a person is young, life is normally care free and worries for the future and thoughts on the past are pretty much non-existent.
As a person reaches their early 20’s not only do they have the stress of taking on the present, but also planning for the future takes up a vast majority of daily routines.
Then, as one reaches their 40’s, not only do you still have the stresses of the present and future, spending time thinking if you have done everything you could in the past also enters the picture.
Finally, you reach a time in life when the future is pretty much a given, the past has become the past and you know nothing will change that, so all you have is to live the present one day at a time.
I think I have finally gotten to that final stage. I know eventually my time here will end and there is nothing I can do to change the past, so I live day in the today accepting life as it comes.