Relationships take patience and effort to maintain. Of course, this does not refer to only love relationships--family, friends, co-workers; maintaining a cordial, if not happy, relationship with them is important.
The level of priority in maintaining these relationships probably depends on how much time you spend with each group of people, and their ability to make your life a living hell. And topping the list is definitely the person you are going to spend the rest of your life with.
There are perks to being in a relationship. You get someone to confide in, someone who cares specially about you, someone you can unabashedly care about, someone you can look forward to meeting, etc. But a relationship is seldom all roses and flutters. Reality always intrudes into the happy picture--be it an stressful day at work, or a random incident that really pisses you off, all has the potential to turn your day into a nightmare. And just when you expect to be rid of all these annoyances, to go home to the arms of your loved one, you find yourself getting into another argument with your loved one.
The problem is this: when you are unhappy, and you bring your bad mood home, chances are that your mood will rub off on those who are closest to you. Some will take it personally, while some shun you for fear of conflict. And you being in a bad mood, inevitably the smallest things will get you riled up.
The solution? Well, there is probably no one solution for everyone, and there probably isn't one solution for each couple. Different circumstances call for different treatments. But the key word is patience. And make more allowances for the person who has a bad day. Sometimes when you are having a bad day, you get a bit irrational, you also want people to give in to you unconditionally. So when you are on the receiving end of it, try to remember that and give in, for the time being at least. You can thrash him when his mood blows over.
Depending on the person, you also need to cheer the person up in the way he/she prefers. For my girlfriend, she prefers to be left alone. Or I will allow her to rant a bit. For me, a hug with comforting words will be best. And the more hugs the better.
Maintaining a relationship that lasts isn't easy, but it will be easier if everyone keeps that goal in mind all the time.