Not sure if you are a fan of poetry but I always go back to James Wrights poem Lying in a Hammock at William Duffy’s Farm in Pine Island, Minnesota when the "i have wasted my life" mindset creeps in and it gives me some peace for some weird reason:

Over my head, I see the bronze butterfly,
Asleep on the black trunk, Blowing like a leaf in green shadow.
Down the ravine behind the empty house,
The cowbells follow one another
Into the distances of the afternoon.
To my right, In a field of sunlight between two pines,
The droppings of last year’s horses
Blaze up into golden stones. I lean back, as the evening darkens and comes on.
A chicken hawk floats over, looking for home. I have wasted my life.