Never think that you're not good enough yourself. A man should never think that. People will take you very much at your own reckoning.

The remark urges self-respect as a practical social necessity: if you internally “reckon” yourself as inferior, others will tend to accept and mirror that valuation. Trollope’s phrasing frames confidence not as vanity but as a baseline duty—“a man should never think that”—because social standing and opportunity are partly negotiated through one’s own bearing. The second sentence is a shrewd observation about reputation: people often rely on cues of self-estimation (tone, posture, willingness to claim competence) when deciding how seriously to take someone. The quote thus links inner attitude to outward treatment, suggesting that self-doubt can become a self-fulfilling social prophecy.