What is a soul mate?

I have been reading "Eat, Pray, Love" by Elizabeth Gilbert and I suggest that all women read it! I have found it very eye opening to say the least! Part of what I read today is as follows:

Elizabeth: "I am not laughing." I was actually crying. "And please don't laugh at me now, but I think the reason it's hard for me to get over this guy is because I seriously thought David was my soul mate."

Richard: "He probably was. Your problem is you don't understand what that word means. People think a soul mate is your perfect fit, and that's what everyone wants. But a true soul mate is a mirror, the person who shows you attention so you can change your life. A true soul mate is probably the most important person you'll ever meet, because they tear down your walls and smack you awake. But to live with a soul mate forever? Nah. Too painful. Soul mates, they come into your life just to reveal another layer of yourself to you, and then they leave. And thank God for it."

Have you had a person in your life that you thought was your soul mate? Is that person still in your life or have they left you? Sometimes I wonder why God brings people into our lives and then I realize that people are like seasons, they come into our lives for a reason and then they are gone. I have several relationships that are just like that (both male and female). They were there at a point in my life when I needed them and then, subtly and without warning, they were gone (moved, died, just lost contact). I often wonder how we "lose" these friendships. Do they not care? Do I not care? No, I think we just change and drift apart! There really is no fault to be placed, it just happens! Will our paths cross again? Maybe so, God willing and then again maybe not!