唯独是你取代不了唯独是你不可取代
[wéi dú shì nĭ qŭ dài bù le wéi dú shì nĭ bù kĕ qŭ dài]
'Only you are irreplaceable, only you are incomparable' expresses that there is no replacement or equivalent for this one special person who is unique in the heart of the owner of this username.