When Should You Give Your Partner a Second Chance?

When Should You Give Your Partner a Second
Chance?

A partner who has professed and pledged undying
love for you in public, private, social media, among
friends and family(even before his ancestors if
possible) is suddenly caught neck deep in an affair –
be it emotional, physical or secret affair.
Take for example, a man who beats his wife for
whatever reason, begs for a second chance. He does
everything possible to win her back until one day, the
devil in him rears it's ugly head again, and he beats
her, yet again. This time he compensates by changing
her car. She hangs on, because she loves him and he
doesn't beat her all the time.
A guy begs his girlfriend for forgiveness after
cheating and getting caught. He cries bitterly, begs
like his life depends on it. Girl sees genuineness,
forgives and they move on. Few weeks later, guy is
back to his vomit.
How do we explain these strange human tendencies?
Do we say it's a weakness that's beyond them, or it
isn't ordinary, or they just want to eat their cake and
have it? Or they don't want to commit to one partner?
When is it right to give another chance? Or is it better
to do away with such people after a first offence? I'll
be waiting to read insightful and honest opinions in
the comment box. And if you've got such an
experience,