Men didn't have any idea about regret
before God felt so once after created us.

I don't buy 'regret' idea.
I need life's good lesson.

Don't live in regret! It is such a useless idea.
Use the memory to prevent us do bad things!
Regret is a childish wish, or an empty hope,
trying to revise the bitter memory of the past.

No need to feel guilty if you can't be a good man all the time. But anytime your heart is feeling so eager to do even a small good deed, then it might be a good chance for you...to be a better man.

No need to feel guilty if you can't be a good man all the time.
But anytime your heart is feeling so eager to do even a small good deed,
then it might be a good chance for you…
to be a better man.

If you believe in predestination, then there is no reason to regret anything. If you believe in free-will, then there is no reason to acknowledge the prophecy. If you believe in both, then you are just looking for an easier way to perceive reality. If you don't believe in both, then you may have an eccentric way of understanding life.