I completely understand the sentiment - 40% seems like a lot to be "burning" for the sake of the other 60.
But it's helped me to think about this in a different context: think about the time you spend with your spouse. How much of that time is taken up with "life's necessities" like doing laundry, dishes, prepping meals, cleaning, more cleaning, driving places, even arguing and getting hurt are all part of relationships... And all that stuff takes time and it's not a nice meal out or a walk on the beach or an impromptu dance session. There's a lot of the mundane in our most treasured relationships, and the only people who have a problem with that are teenagers.
Those "life necessities" in a relationship are not so bad because the goal, i.e. the relationship is (usually) very important to us. The same goes for a job. If you are working on something that has a great value to you, even the boring tasks are usually not so bad. However if you are in a job where the final goal is of no interest to you things change. If tasks are boring and mundane, you will burn out quickly. In effect I believe that anything we do has to have at least something that is important to us, whether it is the journey or the goal it self, otherwise it would be very difficult to keep being satisfied with what we do.
But it's helped me to think about this in a different context: think about the time you spend with your spouse. How much of that time is taken up with "life's necessities" like doing laundry, dishes, prepping meals, cleaning, more cleaning, driving places, even arguing and getting hurt are all part of relationships... And all that stuff takes time and it's not a nice meal out or a walk on the beach or an impromptu dance session. There's a lot of the mundane in our most treasured relationships, and the only people who have a problem with that are teenagers.
Should work/life really be any different?