恨铁不成钢（恨鐵不成鋼）　

◎ 恨铁不成钢 hèn tiě bù chéng gāng

[wish iron could turn into steel at once;(fig) set a high demand on somebody in the hope that he will improve] 比喻对人抱着很大的希望,恨他不长进

这种爱有时候是以恨的形式表现的,这是“恨铁不成钢”的恨,不是“仇恨”