Will Rogers identifies something subtler than merely dwelling on the past—he's warning against the way yesterday's disappointments quietly consume our mental real estate without our noticing. We don't need to be obviously depressed to let regret do its work; we simply make smaller choices differently, second-guess ourselves in new situations, or allocate our attention to what we've lost rather than what's ahead. A person passed over for a promotion might spend months reviewing every interaction with their boss, extracting lessons that feel productive but are really just rehearsing failure. Rogers suggests this accounting is a theft—not of dramatic life energy, but of the ordinary hours we actually have.