1) It may be impossible.
2) You may lack knowledge of how to do it.
3) You may not want to do it.
The first is about the laws of physics, the second the laws of epistemology, and the third the laws of morality. Because people are universal knowledge creators -- they can create any knowledge that can be created -- (2) can only be a temporary obstacle.
(1) can prevent us doing things, but it need not ever make us unhappy. Human problems are soluble within the laws of physics. Suppose we had the ideal world that was physically possible -- utopia. It would be ridiculous to be unhappy about that (especially given that in our present, imperfect society there is already a lot of good). So we can reach a point within the laws of physics which we can be happy with.
(3) can also prevent us doing things, but it can never make us unhappy. If we'd be happy about doing something then it allows it.
(2), despite being the temporary obstacle, is more problematic. We can create knowledge without limit, but there are no guarantees about when we'll learn a given thing. We might have a problem and not learn the knowledge that would solve it for hundreds of years. So to be happy (now) we need a life strategy that can cope with not having lots of knowledge. We can expect to have some knowledge, and some ignorance, and we can't guarantee having any specific piece of knowledge (or acquiring it in under a trillion years).
Fortunately we can get by with an arbitrarily large amount of ignorance. If we get stuck on a particular problem that we can't figure out then we can always replace it with a new one. And if we get stuck again then we can replace it again. We can do this without limit until we find a problem we know how to solve, now.
I may post the method later.