"The rich and the poor have a common bond, the LORD is the maker of them all." Proverbs 22:2
How does that help? you may ask.
God created that difficult person exactly the way He did for a purpose. The purpose wasn't to make your life miserable. The purpose wasn't to frustrate you. The purpose was for His purposes -- the best way that person can shine for Him.
We shouldn't take other people's behavior personally like it is an attack on us (even if it is at times). God is dealing with them and giving them opportunities to grow and learn. And then you factor in the evil side -- the devil and such and only God knows how that person may be influenced by whispers from the darkside.
As Apostle Paul reminds us in Ephesians 6:12, "our struggle is not against flesh and blood, but against the rulers, against the powers, against the world forces of this darkness, against the spiritual forces of wickedness in the heavenly places."
The enemy isn't a person. The enemy is Satan and his crew. He will use any of us to cause havoc in people's lives -- often we don't know we are being used. He wants our eyes off of God and onto our little lives so we get caught up in stuff that is not God. He doesn't care how it happens. He knows God loves us so much and so He messes with us in hopes that it will mess with God (of course it won't -- God is way bigger than the enemy. Nothing the enemy can do can defeat God and stop His purposes).
Does someone make you really angry? Ask God for help. Ask God to help you see him or her as God does. Does someone intimidate you? Ask God the same thing -- to see that person as God sees that person.
There are no relationship issues that cannot be solved with God. Human relationships are messy so sometimes things probably are going to stay messy but God can give us peace about that. And even when we have peace in relation to a person we find difficult we still won't like all that he or she does. But we can rise above it. We can find the humor in things, in people, in ourselves and our reactions to others. We can learn to not take ourselves so seriously and just sit beside Jesus for the adventure.
I'm not there yet but I'm getting there. And you are too.