Blurred Vision

How should you calculate your life?

I would argue on the 'back of an envelope'.

The back of the envelope calculation involves inputting some data but
not all. How can you?
It involves some commitment to finding the answer but is not so
single-minded that you don't find yourself inventing certainty where
it doesn't exist.
It implies the need for certain skills... perhaps critical thinking and
literacy. And recognising that not everybody's opinion on the subject
is equal.
Scientific data is not equivalent to YouTube comments. It is better.
Are we allowed to use a word like better anymore? Isn't that "racist"?
Are we allowed to use a word like superior?
We are supposed to be standing on the shoulders of giants not putting
stones in their shoes.

So when you making your assessments, the "back of the envelope" is as
good a place to start as any.
It leads you to a logic that is fuzzy not fussy.

And you don't need to wait for the postman.
You can get one out of the bin.