我的世界荒芜唯有你是光芒
[wŏ de shì jiè huāng wú wéi yŏu nĭ shì guāng máng]
It literally translates to 'In my desolate world, you are the only brightness'. Through metaphorically saying their life is barren or uninteresting apart from someone's existence which illuminates them like bright light in gloom, it indicates profound affection for that someone.