There is a stiff steel padlock hanging on the door latch. A strong iron rod is trying very hard to break it open but failed. Then suddenly come a tiny little key, with ease... and with its skinny little body, it has open the stiff steel padlock with just a light twist. The iron rod is curious and ask, "how could it possible that a big strong rod like me can't force open the padlock and with just a soft twist your tiny little key can easily open this stiff padlock??" The key replied, "because I have a deep understanding of its heart."
Everyone hearts is like a door locked by a stiff padlock. You can't simply open it with any strong or big iron rod. You need a suitable key of care and love, tender and concern to fit yourself in as a gentle person into that stiff and stubborn heart of another person.