On the half that gets left out
“Everything changes, nothing perishes.”
Four words, and the second pair is the surprising one. Everyone concedes that things change; Ovid's speaker denies that anything is thereby lost.
He means it physically — matter moving between forms — but the line has outlived the physics. What it offers is not survival in any form you would recognise or want. It is the plainer observation that ending and vanishing are different events, and grief tends to treat them as one.