心疼是病但你是命
[xīn téng shì bìng dàn nĭ shì mìng]
It metaphorically says 'being heartache about you might be an unhealthy state for me, but you are the essential part of my life, just like breathing.' This phrase depicts the bittersweet love toward somebody who makes them feel necessary for living, even though being concerned over the person is harmful.