I think the greatest success I've had is in my current relationship, where we're able to bounce back from low times, and where we both realize that our honeymoon period is over, and can still be with each other despite the lack of wuvy-duvy blissful feelings. They're still there, and there is passion- but nowhere near as frequently, but its realistic, I feel proud in it, that it's past a physical, pleasurable time to the point where she is becoming part of my life, not just my sex life or something.
That and for the last 18 months, we have been together through some hard times and bad arguments, yet still at the end of a long work week, can still get together and rip each other's clothes off.