To wear your heart on your sleeve isn’t a very good plan. You should wear it inside, where it functions best.

The remark plays on the idiom “wear your heart on your sleeve,” meaning to display one’s feelings openly. Thatcher’s twist argues for emotional discipline: feelings should be kept “inside,” not because they are unimportant, but because they work best when they inform judgment rather than dominate it. Read in light of her public persona—controlled, resolute, and wary of sentimentality—it suggests a philosophy of leadership that prizes composure, privacy, and strategic self-command. The line also implies that public emotional display can be counterproductive, inviting manipulation or undermining authority, whereas internalized feeling can still motivate action without compromising clarity or steadiness.