What makes something worth doing?
Consider running a marathon by analogy:
Would you a run a marathon without a finish line that required you to run endlessly?
Would you run a marathon that did away with the entire 26.2 miles and merely required you to step over a line?
If the answer is no, then there are at least two elements that make the run worth doing: 1) there is an achievable goal and 2) achieving the goal presents a challenge that requires effort.
It’s unlikely that these two criteria alone fully explain where you direct your energy though: there are likely many things that you could achieve that require effort but you choose not to do.
There remains one more criteria that makes the difference between whether you press forward with an endeavor or not: 3) the recognition that you care — that the accomplishing of a certain outcome matters greatly you and in many cases to the people you care about.
The imperative to pursue things that are worth doing is this: you do not get more time. And the beginning of all meaningful work — the kind that’s worth doing — starts with the same question that only you can answer: what do I truly care about?