I believe in instant love. I know there are different kinds of love... the love you have for your parents, your children, your friends... and your lover, live partner, spouse.
You can't have the same kind of love at first sight that you have after being together for 10 years but that doesn't mean it isn't love.
Some people find it hard to say 'I love you' even after they ahve been together for years, for others it's easy to say after a week, or even after the first time your eyes meet. It doesn't mean that the love isn't love.
I have fallen in love at first sight... twice. The first time ended badly because I was already married and nothing could ever happen.
The second, was also while I was still married but I was unhappy and then, when my husband cheated on me, the man I loved, and continued to love for the 10 years we were together and, in a different way in the 4 years since we've been apart, held me together and we turned our love into something more than it had been.
It's all possible. Maybe not probably but definitely possible. And so, so worth it, even when it doesn't last.