You'd rather be right than in love
. As long as we're talking about how to respond proactively when things go wrong, let's just acknowledge that there will inevitably be times when your partner falls short, makes a mistake or frankly, just blows it. Even though it may seem justified or feel better in the moment, choosing a righteous response will only damage trust and create lingering resentment. Plus, it will teach them to stonewall, deny and argue rather than simply apologize and admit a mistake in the future. It's critical to condition the behavior you want to see by using rewards and not punishment if you want a relationship that lasts.
Take the high road and give your partner the benefit of the doubt, especially if they don't expect or feel they deserve it. It really builds up appreciation, good will and a desire to do even better to please you next time. Bottom line: whenever possible, give people a graceful way to save face when they screw up. Have the humility to apologize quickly if you're the one who screws up. Both habits will go a very long way to creating and sustaining the love you deserve.
[Please note: I am not suggesting you be a doormat and allow outrageous behavior to go unchallenged. I'm simply saying don't sweat the small stuff and choose to stand your ground on the bigger stuff that may be a deal breaker.]