When did you know that your partner was "the one"? Was it something like love at first sight or did they have to grow on you/win you over?

I personally don't believe in love at first sight. I think that's merely attraction. :) In my case, it happened over time. My partner had to win me over. It helped our relationship because it made it more stable and less shallow. :) It also helps to be friends first. I think that allows for a deeper kind of love to blossom and grow.