People are focusing on the asset comment too much, and IMHO missing the forest for the trees.

Let's add one more word:

    Your most important _material_ asset is your ability to produce income.

Bam. No more philosophical/moral connotations. It's almost tautological: your ability to generate material value is your most valued material asset.

It doesn't even have to refer to working as that value generator. If you have enough money in a bank account to live off the interest then that is your most valued material asset!