Love "bears all things..." 1 Corinthians 13:7. This speaks of "putting up with" a struggling Christian even when their actions, attitudes, or words seem to try your patience. This is where remembering where you were when you went through a hard time will help you endure, or "bear" with someone else.
Forgiveness implies "bestowing favor unconditionally" and not holding a grudge towards the one who is receiving forgiveness. In other words, forgive as you were forgiven by Christ.
If someone "has a complaint against another" is the sad description of the behavior of many in our churches today. We thought we got past that stage in our childhood. But all too often churches are plagued with believers making accusations against their church family. What does Paul teach? Forgive! And what else is implied? Drop it! When Christ forgave us He moved that sin into the "Won't Remember Bin" and He doesn't bring that up again. Only the devil, the accuser of the brethren" will bring an accusation against a believer. What does Jesus do? 1 John 2:2, He stands up as our Advocate and pleads our case to His Father. He basically says of that believer, "Their sins are under My blood." Father says, "Penalty already paid. Charges dismissed!"