Well I agree with the guy below me to some degree, but I think tom is talking about how this specific person (marigold) is unable to fit in anywhere and is unable to make any real friends, maybe faking friendship, which doesn't end well(take-backs and sweet regrets). Her relationship with, in this case, tom is a sinking ship, it "hurts too much" to truly be in love with someone, because, as with all her other friends, she will lose them.
That may sound like a pretty shallow meaning, usually streetlight's songs have deeper meanings tha I'm not able to interpret, lol, but I least I tried :)