Aren't we tend to regret things we have done?

Then there come tons of,
"If..."
"I should have..."
"Why did I..."

It's okay, very normal.

Why do we tend to regret things?
Because you see new perspectives, you compare yourselves with others' accomplishments.
Do you enjoy living by seeing other's life as your projection?
Do you think you'll enjoy living like them? How can you be so sure?

No, stop.

Just because you regret things, doesn't mean your life can't be better.
We can do nothing about the past, but we can do something to improve our lives.

Pro tips:
Before you're trying to make things better, it will help your process by accepting yourself first.

Yeah, acceptance is needed, it let us be prepared to walk another step.
Will it be easier? No, easier said than done, always.

Have some faith in yourself.