This won't be long.
I premise that this doesn't mean you should never give second chances, but that in at least 75% of the cases you shouldn't.
Here the biggest reasons you should not give a person a second chance.
They hurt you physically
This goes without saying.
If someone hits you, rest assured it wasn't a mistake and they weren't ''blinded by anger''. They wanted to hurt you, fair and square. And I've learned from personal experience with my first girlfriend, that those people never change.
They will hit you, then apologize.
Then they'll hit you again, and apologize again...
So recognize the abusive pattern and step away from them. Involve the authorities if necessary.
They cost too much
Yes, some people cost too much.
And they'll reach out to you because they want or need money or others privileges from you. With my mother is like that. In those months we have got close again, I estimate she "borrowed" at least 14000€ from me. Money I don't expect to see those money back, plus she asked my fiancée too.
She's not malicious, but she really can't stop leeching off people.
And like her, many people do. Maintain contact with those people only if you are ready to "pay" for them. Literally.
Too much time has passed
They say that wounds fade over time, and only the scars remain.
But scars are delicate and there's no reason to reopen the wound by letting that person back in. Especially if you can't imagine any positive outcome or a healthy resuming of the relationship with that person.
To me it's happening to a friend who had blocked me last year. Now she has unblocked me and asked a common friend to message me to try to talk it out. I said no.
It's a matter of respect. This person probably thinks I'll be up at her beck and call like a dog, and this is not a good reason to reach out. Plus it'd be too awkward and embarrassing. I told the common friend that I would not unblock her and to drop the matter before I block her too.
Weigh down the positives and negatives of letting a person back in your life by giving them a second chances. Most of the time, you'll find out that it's a net negative.
Thank you for reading.