Simplicity and happiness

What do you need to be happy? The answer to this question is a perennial one, because as soon as you answer it becomes outdated, because you'll discover something else that you will believe it will make you even happier. Let's call these the traps of the modern world -the things that will make you most of the times forget about the basics of happiness.
Just to make everything clear, we are talking here about happiness and not about euphoria, the state of mind that precedes happiness but is only sustainable on short term. The reason I decided to make the aforementioned remark, is because most of the people I've met are sometimes failing to make a difference between happiness and euphoria, considering themselves happy only when in an euphoric state.
What's simplicity has to do with it, you may ask. Well, it plays an important role. Why? Well, because most of the times, the people that deep down have the capacity to remain simple, regardless of their position in the society, how high up in the corporation's hierarchy they may find themselves in or plainly just how rich they are, will be the happiest. And by simple I mean, humble, down to earth, with a very well defined and simple set of moral values and most of all true to themselves.
Now let's look at another side of simplicity. I will define simplicity from another angle, that of intellectual capacity. Are the "simpler" people happier than the more complex ones? Or, in another way to put it,are smarter people less happy than the less smart people? In bulk, most of the times yes, because the more complex will always try to better understand what happiness is and what will make them happy, they will try to define for themselves the basic things of their existence without which they will not be happy, while the simpler ones will just take for granted the common definition of happiness: grow-up, have a house, a good wife, kids and the basics for your existence.
I am not a common definition nor am I willing to take it for granted, but I discovered that sometimes we can make our lives less happy because we decide to treat simple things in complex ways, looking for complex solutions, while the solution is staring you in the face.
Sometimes simpler equals happier, no matter how complex you may be.