CW: Esperanto nitpicking
… and would thus seem to be quite opposed to #Finvenkismo (https://en.wikipedia.org/wiki/Finvenkism), an ideological view not all Esperantists subscribe to, but one that is yet rather prevalent in the Esperanto community, so it's a bit unlikely a proverb "against" it would get the broad use one would expect from a "proverb".