Today is my 13th wedding anniversary, and it is about the same time I signed my first publishing contract one year ago. So I have a lot to celebrate!
I'd like to offer advice on how my husband and I have lasted for 13 years when we married so young, but the only advice I can give is to give 100%. It's not a 50/50 split, but 100/100. There will be days he'll give less of himself and vice versa, but in the long run give 100% and don't hold grudges.
Another important factor is friendship. You must be friends in your relationship or, in my opinion, you don't have a relationship. I've gone to car shows and monster truck events because he enjoyed it, and I ended up enjoying it, too. He's done the same thing for me. But it's also important to find something you both enjoy and do it together. I hate to see marriages where the couple goes out with their friends to have fun, but they don't go out with their spouse. It's important to be friends with the love of your life, or how can you like each other?
Anyway, that's my advice for relationships. Simple, really.