I don't think you should buy it; you've been programmed to believe it so that it becomes self-fulfilling prophecy. I think people are more satisfied with life when they have a purpose because they think they need a purpose, but that seems to me like a symptom of a prevalent mode of thought--Heidegger described the modern myth that we work with is that everything kind of represents a flat plane of potential to exploit and turn into utility or usefulness, and searching for some kind of overriding purpose seems like a consequence of that.

I think you should just explore religion (esp. Zen, Dzogchen, Mahamudra, Advaita), philosophy, literature, and yourself through first person experience until you intuitively feel the error of this entire mode of thought. It won't do to tell yourself that, although reaching the conclusion analytically makes for a first step. You have "meaning" and "purpose" sapping assumptions built into you, like modern materialist reductionism. Reductionism says that a thing amounts to the sum of its parts, but it's obviously fallacious. Try cutting a cat in half and putting the two parts back together and seeing if you have what you started with. Reductionism is a powerful mode of thought in certain circumstances, but it's not absolutely true.

I think we need to acknowledge what there is outside of ourselves, and recognize that the universal is always and only found in the the particular. Every blade of grass is alive with meaning, but it doesn't speak it in terms of utility and materialist reductionism.