Almost 41 years for us. Married right out of high school. My dh took a sociology class on family his last semester in college and came home and told me we had no chance. We did everything wrong. Here's what I think made it work so far:
1. Be willing to forgive
2. Make the other person important in your life
3. Do things together, but have some interests of your own
4. Be too stubborn to give up
5. Don't take any nonsense