Let it be like a line drawn in water rather than sand or rock. Every wrong to us is ultimately meaningless and impactless except as far as we react to it personally as a painful rather than powerless thing. The pain is usually from the belief that it should be painful because... because... because... etc. with because becauses. These when chased to their most fundamental "because" are ultimately groundless beliefs usually conditioned in people by society, and belief, a particular kind of cognition, can strongly drive emotional reactions - especially stuck ones that persist or sting for a while - that otherwise wouldn't be there without those beliefs. This may be a bit of stoicism, but I have lived this truth. Even more strongly, to support this with the Bible, Jesus is ultimately the only thing (*person) that matters in life. What ever happens to us, we have Jesus, unless we don't because we made the wrong choices (usually out of hurt and bitterness) and commit sin leading to death.
Still, I'm sure God's Word instructs or commands forgiveness only when the person who sinned against you repents - and forgive always when there is genuine repentance - as we are forgiven only with repentance. If forgiveness from even God is conditional, then why should we unconditionally forgive? Not forgiving does not mean one has to harbor resentment or bitterness or continued anger - these things should not drive not forgiving / unforgiveness - just the lack of repentance of the offending party. If the offending party does not repent, one should determine whether or not to have any further interaction or anything to do with them, lest they be a stumbling block for one again. If one never sees them again, they don't have the opportunity to repent, and one does not have the opportunity to forgive them. If one does see them again not having rebuked them in love soon/immediately after the offense back then and gotten repentance from them, then see if they have repented in their heart in how they treat you and forgive them, probably silently in your heart, or bring it up to them directly how they have wronged you, and see if they genuinely apologize and genuinely repent. Then it is good to forgive - otherwise if they just treat you wrong or keep wronging/betraying you, it is just best to get them out of your life if possible.
I hope this helps anyone who reads this, I know it is often a disastrously-poisonous, bitterness- and resentment-generating unwritten rule of society that one should always instantly and unconditionally forgive no matter how horribly one is treated for no matter how long - when the Bible seems to state otherwise :-O ! Good luck

!