5. Always be ready to give the grace of forgiveness.
You will sin against one another. You will hurt each other. That is a given due to the power of your sinful flesh. At this time in your relationship begin to cultivate a spirit of forgiveness that is always ready to honestly say, "I forgive you." Those three little words, which some people who've been married for twenty years have never said to each other, will wipe the slate clean and prevent walls from building in your relationship. An angry or unforgiving spirit builds walls between people-one brick at a time. Every time you sin against each other choose to shatter that brick by means of biblical confession ("I sinned against you. Will you forgive me?") and forgiveness ("I forgive you."), rather than cement it to other offenses which only build a wall of resentment and bitterness in your heart and, consequently, poison you and others (trust me, I do a lot of marriage counseling). Repent of sinful attitudes whenever they arise. Every day take your relationship back to a hill called Calvary.

And so, as those who have been chosen of God, holy and beloved, put on a heart of compassion, kindness, humility, gentleness and patience; bearing with one another, and forgiving each other, whoever has a complaint against anyone; just as the Lord forgave you, so also should you (Colossians 3:12-13).

...do not let the sun go down on your anger, and do not give the devil an opportunity (Ephesians 4:26-27).