The way I usually relate this to my congregation is that we must preach the gospel to ourselves everyday. At the very least we must train ourselves to keep it before us and make it part of the way we think about things. Not only does this cause us to keep a humble and thankful heart before our Lord but it also helps us maintain the proper attitude in which we can interact with others in Christian love.
Matthew 18 is a chapter in which this is taught to us by the Lord. He begins with the reminder of how only through childlike humility and dependence can we enter and live effectively in the Kingdom of God. Then he teaches us of the necessity of humility and a forgiving spirit when it comes to living with those in the church and exercising church discipline. Finally he ends with a parable that shows us how to be patient and forgiving with others or to do all the things he has just taught us.
It is the story of the unjust servant who was forgiven a debt that could never be paid yet was impatient and unloving towards those who had but a relatively small debt to him. We see it in the Lord's word to him as he calls him to account for the way he treated his fellow servant. Mat 18:32 Then his master summoned him and said to him, 'You wicked servant! I forgave you all that debt because you pleaded with me. Mat 18:33 And should not you have had mercy on your fellow servant, as I had mercy on you?'
What he is telling the wicked servant is that he should live his life in light of the mercy and love shown to him by his Lord. A lot of our problems with relationships arise because we think we deserve something we don't. By reminding ourselves that it is only by the grace of God that we are not in Hell at this moment and so every breath we take is undeserved, we are reminded of the greatness of our God and seek to please him by showing the same love to others. When we make ourselves the center of our lives we immediately come into conflict with everyone else who lives the same way.