First, I think the Bible gives us very good scripture about how to relate in love and friendship >
Ephesians 5:21 > mutual submission in submission to how our Father guides our relating
James 5:16 > mutual confession with mutual prayer for healing into how God's love has us relating with Him and one another
Ephesians 4:31-5:2 > being "tenderhearted" with one another, "forgiving one another, even as God in Christ forgave you." Being all-loving like Jesus was sweet-smelling during His sacrifice on the cross . . . being sweetly kind . . . and pleasing to our Father, about how people were hating and torturing and killing Him!!!
James 1:19-20 > "swift to hear, slow to speak, slow to wrath" > "the wrath of man does not produce the righteousness of God." You may need your friend so you can practice to be perfect in this
We can tend to connect with ones who, really, are like us, but "different only in the details" . . . details of how we, too, can be selfish, thus needing to forgive "each other".
Mark 11:25 > forgiving in prayer "for" the ones we forgive, in caring love with hope for them > see also Luke 23:34, with 1 Corinthians chapter 13 about real love.
And Ephesians 4:2 says,
"with all lowliness and gentleness, with longsuffering, bearing with one another in love,"
So, I need to be strong, "with longsuffering", so I can bear with how others are going to be wrong, somehow. Even really Christian people will at times be wrong; this is "why", I consider, God includes "with longsuffering" in how He knows we will need to be relating
And > "nor as being lords over those entrusted to you, but being examples to the flock." (1 Peter 5:3)
So, if someone is wrong, you need to first be in prayer and "longsuffering" so the person can not have power over you to effect you the wrong way. Then first be good example to the person, relating the right way with him or her. This can show the person that their wrong way is not going to control you and have power over you, but you are there for them with love, not going to give up on them . . . like how God does not give up on you
And if your example doesn't help the person, you can say something and see if the person is able to deal with it. If not, how are you going to stay with the person, anyway, if the other is not able to do things right?
"Just make sure that your being hurt or irritated is not because of your own ego being wrong."