How can you expect to obtain happiness when you are always busy to want what you don't have? It simply doesn't work that way! You are always running towards a carrot that you carry with you, no matter how far you go. You can't escape the hedonic treadmill that way.
The only escape is to want what you already have. It is this what is called with different glorious names like savouring or gratitude. The idea to become happy once you just get that something more that you desire at the moment is an illusion. It keeps us running forward, but it's making us miserable, because we don't the scenery surrounding us. More importantly it distracts us from enjoying ourselves and what we already have. And that's not little. Everyone has her own life, at least. In our current age, we also have our own bodies. And if you can understand these words, you have a marvelous brain and wonderfully functioning organs that support its function. This thought is everything you need to spend the rest of your life in bliss. Yet, you don't. Why? Does this feel like an illegitimate hack? No, the only kind of happiness that is really sustainable is that which you obtain by hacking your own happiness! Try something different, and the hedonic treadmill will quickly evaporate your happiness.
Happiness is a choice of perspective
It's really simple. There is a virtually infinite number of things that could be "better" in your life. At the same time, there is also a virtually infinite number of things that could be "worse" in your life. If you consider the first, it will make you miserable, because you compare your current situation with something that is so much better, so your life will seem relatively bad, which will make you unhappy. On the other hand, if you consider the latter, it will delight you, because you compare your current situation with something that is so much worse, so your life will seem relatively good, which will make you happy.
This isn't any kinf of new insight. The ancient Stoics already knew that. So they made it a habit to imagine horrible things happening to them. That those horrible thigns most often didn't come to pass, made them rather happy. We could do the same, but we are stupid and distracted, so we don't. How pathetic is that?
So what? I don't want to be happy
Perhaps true. What if you goal isn't happines, but something else? Well, in that case, you still might want to be happier, because happiness comes with functional benefits. All other things being the same, being happy, generally makes people more successful, more resourceful, healthier, and more creative (citation needed). Being unhappy is not good for your brain. You need to be mindful of your psychological and neurological hygiene. Be happy, or get sick. And that's not moralizing, it's how our biology works, no matter whether we like that or not.
But I have more important things to do than being happy
Yes, and you also have more important things to do than to brush your teeth, eat food, drink, breathe, excrete, and do exercise. That doesn't make it a bad idea to actually do those things! Done in right moderation, these activities will improve your life a lot. Trying to eliminate them from your life usually ends in catastrophes.
So, perhaps it's the best idea to make being happy a part of your daily schedule by actually mindfully want what you have. It's worth a try, at least.