Wanting something, the speaker says, puts you at a disadvantage. Desire makes them weak, while having no desire makes them strong. But the speaker does want something: the strength they see in the other person. The trouble is that the only way to get at that strength is through the other person's weakness, which is their desire for the speaker.
So the poem sets up a small loop. Each person is strong only when they don't want, and weak when they do, and each wants what the other has. The title points to the psychological ideas behind this, with desire as a kind of lack, but you don't need to know any theory to follow the logic.
The tone is cool and clipped, almost like a proof worked out line by line. The short, flat sentences make love sound like strategy rather than warmth. Then the last line brings in the yin-yang, which makes the whole thing feel both neat and a little dizzying, since the "whirling" never settles on a winner.