我会穿着葬服参加你的婚礼
[wŏ huì chuān zhe zàng fú cān jiā nĭ de hūn lĭ]
This translates directly to 'I will attend your wedding wearing funeral clothes.' It reflects dark and dramatic romantic despair—implying bitter resignation that their future with this person involves sadness rather than joy. There's also an implication of disapproval or being excluded from the happiness associated with marriage.