Board Thread:Show-Related Questions and Answers/@comment-26116863-20160926025050/@comment-28162607-20180717184825

Love has to exist on both sides, yes, but if it's a curse (and TLK is always on a curse) as Belle said, it only works when the person wants it to work. Which is why it did not work for Rumple and Emma; they liked the power and wanted to hold onto it.

The Snowing forehead kiss was just weird. It should have broken the curse.

I think for the Dark Curse, belief was required too since Snowing were kissing left right and centre and no curse broke.