I think the meaning behind this is not to build relationships up too high. Some people, like myself unfortunately, build alot of things up on their relationships. Expecting something meaningful out of it, but it's not always like that. Sometimes, doing this can lead to you always freaking out "I decided to name her insomnia". Worrying where this person may be, when they'll call, when you'll see them again, and such. Also, the "this I must tell you, old friend: fear beauty" kind of hints to me that beauty does not equal love, and that thinking like that can not only be hurtful, but can put you in a bad situation. - This is just what I think, I have no idea if this is the true or real meaning behind the song. If you'd like to know that, I suggest you ask Mike (The Devil Wears Prada) himself.