I'm 19. Not very old to be giving advice, but old enough to give a little. My experience will have been different than yours will be of course. However, there are some things that should always be apart of a relationship. Especially in boyfriend/girlfriend relationships.
1) Selfless. In every relationship ALWAYS think about the other person first. Even if they're completely wrong. They come first. Then you.
2) Be honest with the person. I have a hard time with this. I tend to be honest when I know things will be all right. And tend to not tell things when I know they won't be. It's hard because even though we could be trying to protect them, we're only hurting them and ourselves.
3) Being humble. Even if you are completely right about something and you know it. Humble should be your default mode. Seriously. Ask yourself "Did I do that?" or "Could I have done that? Is it a possibility?" Anythings possible. So put the other person first and be humble about it. Even if you're right. Because whats more important? The person or you being right? I thought so...
4) Protect. This doesn't always have to be physical protection. It can mean protecting the other persons emotions, protecting him/her from being hurt by others or yourself.
5) Forgive and Forget. Literally. Don't bring crap up to rub in the person's(you care about and love) face. If they're sorry for what they did and you forgave them than by all means let it go! It won't get you both anywhere and end in constant fighting and hurt. Seriously...let it go.
6) Do kind things for them. Surprise them, give random gifts, go have fun with them. Laughter is good. Talking about serious heavy stuff all the time will turn the relationship in to serious and heavy.
7) Be patient. I feel like this one is self explanatory. I'll say a word or two though. Give the person time. Don't expect changes over night, or even for a long time.
8) Listen. Hear. Understand. Those 3 words will keep a couple together. Yeah, you can listen to someone. But can you hear them and have compassion and feel what they're saying. And understanding is simply telling them you care, and even doing something about it.
Have you noticed I haven't mentioned love? Know why? Cause all of the above IS Love. Love is all of that and more. I struggle with every one of those. But at least I know and I strive to do each of them and more. Relationships are tough and exhausting at times...but the reason for that is because we are selfish people. And relationships are all about being selfless. Crazy huh? Its about sacrifice and doing things you do not want to do because we always want ourselves to be first. It pays off though you know...and in times gets better. Anyway just thought I'd share. Take it or leave it.