I can only speak for my own - we'll have 22 wonderful years in a couple of weeks. We've gone through poor times, good times, lots of money, "what are we going to do about our lack of money?", births, deaths, incredible joy and sorrows that made us ache. We often have pissed each other off, argued/fought, and -gasp- gone to bed angry.
But all of that has made us closer than ever, and I love her so much that I realize I didn't even know what love was when we were married. The key is that our marriage isn't based on a "me-me-me" foundation. We've seen marriages of friends fall apart because one of the spouses felt "they weren't getting what they needed" from the marriage. It's a self-centered world these days, and that's murder on marriages.