It's fascinating to me how many smart people fall into this trap.

Can they quantify their love for their partner? No? Well, I guess they have to give up any efforts to improve the relationship.

"If you spend 10% less on birthday presents for your children, will that make them love you 10% less? How can you justify spending this much on presents?"

there's another issue with measuring too much: if you only derive value of that you can measure, you will constantly feel bad when doing things that have no apparent measurable value. So then you say to yourself, relaxing on the sofa has value because it makes you perform better to have breaks. But do you really believe this? And in any case, you still can't help measuring value into relaxing because you are brainwashed into thinking everything must be quantified in order to justify something. So even relaxing or playing video games must be seen in such a context in order for you not to feel bad. it's becoming rediculous.

I also like to point out in a few similar contexts: even if you could measure all the things, and you could create a perfect/optimal cost function, there would still be no guarantee that you'd be able to find the optimal global solution. So relax.

"the most important figures that one needs for management are unknown or unknowable" -Lloyd Nelson, quoted by Deming.