My Two Dogs
I had two dogs growing up.
One was part poodle and one of the smartest dogs I've ever known.
The other was a long-haired chihuahua and, while not dumb, he was clearly more instincts than intelligence.
Why do I bring this up?
Because one was miserable and aged terribly (age spots, bad cardio, body growths, hair loss, and peeing herself at night). We had to put her down.
The other lived longer than any dog we've known. Even when his body started to go in his old age, he was still full of energy and happy to see you.
It was the smart one that was the most miserable. You could tell she was always thinking. What about the "dumb" one? He was always in the present moment.
They both went through bad times. The smart female got spayed and she was never the same since (it's like she somehow knew she couldn't have children anymore). The instinctual male lived with my brother several times and each resulted in him getting bullied by another dog. You could tell it was really stressing him out.
But the chihuahua bounced back like nothing happened. He didn't bother with the past, he just stayed in the present. He was always looking for food or for dog butts to sniff. The poodle, on the other hand, would just lie down and think all the time.
In this life, everyone suffers, but only those who can realize that is in the past are the only ones who can be happy. There is no other way.
That's exactly what my chihuahua did (actually, I think the dumb dog completely forgot, if only we could all be that lucky). He just let himself focus on what now made up his life.
He focused on action, not thinking.
Want to be happy? Then don't think about your life, go out there and live it!