A few years ago a young Christian man used to stop in Oasis often on his lunch break. One day he came in angry and announced that there was no hope for a certain named person. I asked him what made him say that, and he told me the story. He said that he and the other man played together on a Christian softball team and they had gotten into an argument. The other man had picked up a baseball bat and threatened him with it. From that point the conversations reflected the following. See if you can relate.
Me: What he did to you was really sinful.
Brother: No need to tell me.
Me: Is he a Christian?
Me: Has God forgiven him for all his sins?
Brother: Of course.
Me: Is God counting his sins?
Me: Then why are you mad?
Brother: I am counting.
At this point the conversation changed and the brother relaxed realizing that his problem was that he had forgotten how God viewed the other Christian. Also he admitted that he had been angry in the argument. We rejoice together in what Christ had done for us all and he said that he would call the brother that night and admit his wrong even if the other brother didn't. The next day he came back and said that when he called the brother, the brother was in tears confessing his own sins. The rest of the story is that these two men became fast friends. Grace is powerful.
Unmerited favor takes what seems a hopeless relationship and fills it with hope of the gospel, not of personal performance. But it is not automatic. It requires remembering the freedom Christ has given in His work on the cross and understanding what that all means. Do you have any troubled relationships with Christians? Talk to God about it and tell Him how bad the other person's behavior is. Don't minimize it--maximize it. Tell Him that the person deserves hell for that sin. Thank Him for the cross freeing that person from what he deserves: from all condemnation, guilt, shame, and score keeping. Maybe even thank Him for smiling down on that other person who troubles you so much. Try it and see what happens. You might find you actually like that person. Miracles do happen.