Why I won't be marrying my best friend

How close are you to your partner? In my early twenties, there was this one line that was drummed into my head in regards to marriage; get married to your best friend. This got me looking at my closest male friends a certain way. I got so confused about how to treat them.

I have never fallen in love with anyone I considered a best friend. Maybe I have fallen in love with a friend but I have never held onto a friend long enough for him to become my best friend then fall in love with him. You see, I fall in that group of people who find love from strangers.