For me, the difference is the level of emotional attachment. I could go days or weeks without any interaction with my friends and be fine, but with any girl I've liked, I've had to get some attention from at least every other day. Another thing would be how close you feel. With friends it feels as if there's a glass between us. And I'm fine with that, because I like my privacy. Thing is I need one person I can share everything about myself with, and be able to feel safe about it.
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About suffering they were never wrong,
The Old Masters: how well they understood
Its human position; how it takes place
While someone else is eating or opening a window or
just walking dully along...