If you're looking for euphoria, strong emotions of happiness, I do not know. (drugs might do it? alcohol and weed don't.) If you're just looking to be happy, as in content with life, I think it's something that can be 'easily' achieved, but 'impossible' to maintain. By that I mean you'll never be happy all the time, no matter how hard you try. You can be content most of the time, simply by thinking and pursuing your own personal goals. Give yourself the time and space to do so, never push yourself or stress yourself. I know people say it's good to have high expectations of yourself, to push your limits, but I do not agree. Do what is necessary, then do what you like. Enjoy yourself, at all times.
While 'getting a career where our natural assets are valued' would be a nice start and a good thing to have, by no means is this equal to happiness. We live up to standards. Our own standards, set by our expectations. We all want happiness, but we seek it in various places. We all find it, and yet nobody truly does. Some want money, some want power, some want relationships, the list goes on. The truth is, it's not about any of these things. It's about 'getting what you want'. And once you get it, you'll be happy for a while, and then you'll desire more / something else. While you can realise this chain of events releasing drugs into your brain, you cannot escape it. (Doing actual drugs is a subpar bypass at best.) That being said, you can influence this chain of events heavily.
So I assume your question is which are our desires, as opposed to other types. Again, we all want the same. We all, somewhere, want to be and feel loved, and we want to love others too. We all want good jobs, and we all want to be appreciated. (And for the serial killers, we all want to kill that annoying neighbour.) It only becomes truly important, however, when we expect these things. When we pursuit them.
As INTPs, I assume most of us claim we don't need or want relationships simply because we have a difficult time finding and maintaining them, so we believe they're just 'not for us'. Since we're not emotionally strong, they're also simply difficult. We are good at intelligence, however. I'm sure alot of us aim for the pursuit of knowledge, being recognised by others in this could be, but does not have to be a factor. We choose our pursuits based upon what we're good at, what we do and drives us, and in turn we depend our happiness on our pursuits. You choose your pursuits. You choose your happiness.
The most important thing regarding happiness, however, is valuing things properly. Imagine you do not pursue a relationship, because... INTP, and instead strive for knowledge. But somehow, you end up having a good relationship, you get a family and lose track of your pursuit of knowing all the things. And then your midlife crisis of not having completed your teenage dreams hits you. I ask you, should you be unhappy because you got a great wife and two kids instead of winning a nobel prize, or just be happy with the things you've gotten, while you can still pursue everything else you want? The only thing stopping you from doing all the things you'd ever want is time. Because there's only one constant... It's never enough, we always want more.
The key to happiness is to happiness is to control your desires and to value what you have.