Making it last

What's the best advice you've received for making a relationship last? For me, it was awhile back, my boyfriend and I met a man who had served in the military for 15 years, who said that he saw in us the love he always wished he had. He asked me if I thought my relationship with my boyfriend would last for the long haul, and I said, "I hope so". He stopped me, and said, "No, you know so." I smiled, and took his advice. It worked. I've never been happier with another person, and I know that I will be happy with him for the rest of my life. :)