Above all, keep fervent in your love for one another, because love covers a multitude of sins.
1 Peter 4:8
If you find yourself easily annoyed, the certain cause is a lack of fervency in love. The majority of my mistakes in dealing with people is because of not adhering to this command.
1 - Pray for this person specifically and often. Ask God to bless them and to use you to do it (and mean it!)
2 - Look for ways to serve them. Find a way to lay down your life for them. If you can't find anything to do then make something up.
3 - The main help: Spend quality time with the great Lover of Souls - the Lord Jesus. I am ashamed and humbled every time I get a glimpse of how much He loves in comparison with how much I love. I have given Him every reason to be annoyed, but I have never found Him so. We must never get used to that.