Often, when a couple has been in a committed relationship for awhile (even if they aren't married yet!) they can become complacent. You settle into a routine, things become "normal", and you stop feeling butterflies every time you see your significant other.
The importance of planning for your future.
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For better, for worse, forever!
Some of the best advice I ever heard for a relationship was to compliment your significant other during a fight. This has a two fold effect: first - you will stop saying angry things and fueling the fire of the fight, second - you will remember what you love about that person and begin to soften your heart to what is making you upset.