It turns out the end of the movie Speed was wrong:
Jack: I have to warn you, I’ve heard relationships based on intense experiences never work.
Annie: OK. We’ll have to base it on sex then.
Jack: Whatever you say, ma’am.
In fact according to several studies — some of which (PDF) are mentioned in this article from You Are Not So Smart — couples that engage in “intense experiences”, as Speed put it, report higher quality relationships. The psychological explanation for this depends on two concepts:
The first concept says that what motivates us to do anything is a desire to expand our boundaries, to grow, to acquire new skills. So when we do things that are challenging, new, and exciting, we feel truly alive. That state is known in psychology as “arousal“, of which sexual arousal is just one kind. So when you go bungee jumping, the fear and exhilaration present means you’re psychologically aroused — that you’re firing on all cylinders and really experiencing the moment. This state of arousal is what we tend to like, and when we get there while with someone we also like, we associate them with the experience. If that keeps happening, classical conditioning makes us associate them with the psychological arousal, which makes us think the relationship is the source of all the good mental state and therefore makes us want more relationship. Kind of like falling in love with your drug dealer.
What’s even more interesting is that just spending generic time together with a spouse doesn’t have any effect on the quality of the relationship; it’s the challenging and exciting things that matter. So if Alice and Bob go on a romantic candlelit dinner, followed by a quiet walk on the beach and the end, it won’t be as good as if after walking they went skinny dipping in the ocean where they saw a shark while making out, and Bob scared it away by punching it in the nose and then they ran out of the water, but their clothes got blown away by the strong ocean wind so they had to break into a shop on the beach and steal some bathing suits, because it’s better to be arrested for shoplifting than public nudity — or at least it seemed better at the time. And then on the second date (yeah, that was just the first one) they go to see a scary movie, and on the third they go to Busch Gardens and ride the roller coasters and on the fourth they go skydiving, and before you know it, who comes knocking at their brains’ doors? Pavlov.
Alice and Bob will associate the relationship with all of these highs, and just like in Pavlov’s experiment where the dogs learned to salivate when the bell rang because bell meant food, so does Alice learn to mentally salivate when it’s time to hang out with Bob, because Bob means excitement, challenges, and ultimately self-expansion. This particular effect is known as “misattribution of arousal”, though we misattribute other things too — for example if you nod to a guy that’s talking about stuff you don’t care about, you’ll later tend to think you agreed with him.
So what’s the practical take-away from all of this? Well, the psychological arousal is what really makes you happy, but it’s kinda sad to go to Busch Gardens alone. So instead, do novel, exciting, challenging things with someone you like, because you’ll like each other more due to the arousal from those activities. And don’t ever stop, because then you’ll fall in a rut and get bored and then also misattribute the boredom to the relationship and start hating it.