柠檬心不曾为你酸
[níng méng xīn bù céng wéi nĭ suān]
This username implies a bittersweet love that didn't cause heart pain. 'Heart of lemon' suggests a mix of sweetness and acidity (ambivalent emotion) in a relationship. Here the user wants to convey that no matter how special you are, my heart is not influenced by you and has maintained its independence and detachment.