The Kural in life
The two directions of a life.
Every choice nudges you one of two ways: toward becoming someone, or toward quietly coming undone. The verse draws that axis starkly — virtue is the greatest gain, and forgetting it the greatest loss. Not a dramatic fall, usually, but a slow forgetting: the standards you stop keeping, the small honesties you let lapse.
Loss by forgetting, not by deciding.
Few people choose ruin outright. They simply forget — get busy, get distracted, and stop tending the thing that held them. Valluvar's word is precise: not 'rejecting' virtue but forgetting it. The danger is not a villain's choice; it is inattention, which is far more common and far easier to slip into.
The ledger nobody else sees.
You can hold a reputation while the inner account runs dry. Other people read your results; only you know whether you are still keeping faith with what you believe. This verse puts the real profit-and-loss there — in whether virtue is remembered or quietly let go.
The verse names both the greatest gain and the greatest loss.
Having said virtue is the highest gain, Valluvar completes the thought with its shadow: there is no greater ruin than forgetting virtue. He pairs gain and loss so the choice is unmistakable — and chooses the word 'forgetting' deliberately, because that, not open rejection, is how most people lose it.
Guard against drift, not just against wrong.
You probably won't decide to abandon your principles; you'll just get busy and stop tending them. Treat that quiet forgetting as the real risk. Build small reminders into your week so the thing that holds you doesn't slip out of view.