What's the best piece of relationship advice?

From learning to listen to being a team - what's the best piece of relationship advice out there?

Reddit have been at it again, asking people from around the net to reveal their top bits of relationship advice. This makes for some pretty interesting reading.
"Be a team. Most couples don't know the right way to fight (and there WILL be fights). Don't worry about which one of you is "right." Remember that it's you and your partner vs. the problem, not you vs. your partner. Source: married 30 years."
"A relationship can't work when people are always thinking "what are they doing to make me happy". Instead, both partners need to constantly be thinking "how can I make them happier?". It's the real secret to marriage. Kill them with kindness."
"Something my girlfriend and I do, that she brought to the table, was the sign language sign for I love you. In a loud or big place I can still tell her I love her from across the room. It makes for a really personal moment amid the chaos. Highly recommend it."
"Invest yourself. Everyone always says "don't get too invested, it'll only hurt when you get burned," but you know what? The greatest things in life were built over time, through hard work and dedication and passion. If you want to build a relationship, start with a good foundation, and don't quit until you're done. Make the relationship your passion-child, and put every drop of emotion your partner deserves."
"Talk to your spouse and stay positive as often as possible. Those two things will make any relationship function better than someone who is closed off and bitter."
"This is cliche as hell, but don't ever get into a relationship with someone who you wouldn't be very close friends with outside the context of a relationship.
Ask yourself some questions: if you weren't in a relationship with this person, would you still enjoy their company as much? Would you still find them interesting? Would they still be a person that you'd actively enjoy being around? Would you get along well if you were both strangers?"
"Learn to listen rather than talk over one another. Communication is key to a great relationship."
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"Accept that it's not going to be roses and rainbows all the time. Accept that it may be your fault when that happens. Do your best to communicate effectively to minimize misunderstandings.
Nurture the relationship, but don't lose yourself in the process."
"Don't assume anything. You may know a person quite well, but you're both still individuals. Communicate rationally and try not to act in the heat of the moment."
"You will have a more successful relationship with someone who shares your values versus someone who shares your interests."