Not the First Man, Not the Last

Talks about suddenly becoming madly in love with this beautiful girl you just met. She looks like the image you had created in your head. She gives you everything at once, like all along she had been waiting for you. Then you realise it was all a passing fancy, more for her than for you ("You're not the first man, and you won't be the last"). You also learn you were in love with your own idea of who she is ("She's mine"), and not the girl herself.