There is no question that there is an association between stimulation and sex, and that stimulation during sex is important. However, if you're in a relationship, it's even more important to understand what besides sex stimulates you and why. If you don't know what stimulates you, or alternatively, turns you off, how can you expect your partner to know?
For example, I like to go to sleep at night without any noise. That means no television, radio, or internet videos or movies. On the other hand, my husband prefers to fall asleep with the television on, especially if there is a sporting event. Now, my husband may tell me there is something specific he wants to watch on television, but the reality is that he generally falls asleep in less than 10 minutes. As soon as I hear the change in his breathing I reach for the remote to turn off the television, but inevitably his hand shoots out to grab mine and he says "What are you doing? I was watching that." We then engage in the circular conversation that starts with "No, you were sleeping." Although he really did fall asleep, that isn't the point. The point is that while the television is white noise and soothes my husband, it stimulates my mind and keeps me awake. The ability to recognize the reason behind our likes and dislikes regarding something as insignificant as having the television on at night, has allowed us to change the focus from something we cannot necessarily control, i.e. our internal stimuli, to something we can control, i.e. making compromises.
Instead of having a general disagreement about whether the television should be on or off, it's about whether it's something that he really wants to watch, i.e. the Royals in the playoffs, which ended up being a few weeks of very late night television due to the perpetual extended innings, or the fact that I'm exhausted and really just need to be able to fall asleep.
The interesting thing about stimulation is that it is huge component of every relationship, and most people never think about it. Your likes and dislikes aren't just about things that interest you. They are about things that stimulate your mind and your body. If you aren't stimulated you get bored, and boredom can result in consequences that run the spectrum from changing jobs to having an affair.
So, how do you stay stimulated? That's the big question. What stimulates you at 20, will change when you are 30, 40, 50 and beyond. What's important is that you recognize not only what stimulates you, but also what stimulates your partner. If you start going in different directions, PAY ATTENTION. Life gets in the way, and if you don't pay attention you can wake up one morning and discover that you've not only forgotten the definition of stimulation, but also completely disconnected the concept of stimulation and your significant other. Sex and stimulation are always good. However, negative stimulation is not good. Instead of immediately reacting to your significant other, take a minute and see if what is positively stimulating to you is either negatively or not stimulating to him or her.