Many people just don't value themselves.

Perhaps events through their life, whether it is childhood memories, bullying, or being controlled by a partner, have made it hard to see their own beauty.

Perhaps it's guilt from previous behaviour.
Remorse in itself is damaging. Other than the experience showing us a better way it serves no purpose. Let it go. Make amends and move on.

All experiences in life are just that: experiences. We learn and grow from them, and are better people because of them. Every single interaction with people teaches us something.

As Thich Nhat Hanh says "Even a lotus flower needs muck to grow".

You are a child of the universe, you have every right to be here and have as much value as anyone else.

Let me help you see that.