Good Advice (from Virgil - or Apollo)

VIRGIL, from Eclogue 6

Cynthius aurem
uellit, et admonuit: "Pastorem, Tityre, pinguis
pascere oportet ouis, deductum dicere carmen."

From the translation by C. Day Lewis:

Apollo tweaked my ear,
Telling me, ‘Tityrus, a countryman should be
Concerned to put flesh on his sheep and keep his poetry spare’.