It's really hard when you do something unforgivably callous to somebody yet they still forgive you anyway. After that moment, the guilt will haunt you for the rest of your life. I mean, sure it'll be negated by time but the point is, it's there and it will never go away. It's like a crumpled paper that no matter how much flat pressure you put to it, it'll never go back to its original state.
Once you wrong somebody to an infinite level, but eventually just let you off easy, being around them will never be the same. It's like your behavior towards them or simply how you treat them will completely change into a safe mode kind of way. That's because you're scared you might do something wrong to them again.
Worse, even if they're the ones to do something bad to you, so long as it never goes to the extent of leveling to what you have done to them, you have no choice but to let it just slip. You give an entire world of not giving fucks to anything offensive that they may do to you. Because once that happens, you'd think they'd most probably slather all over your sorry ass what you did to them. The thing is, you will always feel mortified around them.
So, always be careful in things that you do. Never do anything that you will eventually regret for the rest of your sorry life.