Unless you are rich enough to have chosen it, or maybe a prisoner, you always have more than one thing to do. Laundry, groceries, complex engineering, it all needs to be done.
I think our minds evolved to track all these things and, probably in a time sensitive way more than projected future value, to prioritize them. For this reason, I think having multiple projects is the natural state as the mind is optimized for this. So maybe this is the "best way" and explains a lot of the strange ways in which putting a problem aside can help solve it.
