Setting aside whether I actually like the song or not, I think the song that best describes me (at least among the ones I've heard so far) is "Lucky" by Britney Spears, in a metaphorical sense that is. People often tell me that I'm good at various things and have great potential to succeed in life, but despite all those things, I often cry for no apparent reason. This goes well with the last two lines of the chorus: "If there's nothing missing in my life, then why do these tears come at night?"
Another song that resonates with me is "Dust in the Wind" by Kansas. I often feel that notion that everything that happens in life is fleeting, that it soon vanishes into a void, that a person's individual actions are altogether meaningless... especially when something really good happens in my life. I remember that good thing, but feel as if it had little impact on my life and especially the lives of others. I know too well that one person's actions have little impact on the world in general, and that often depresses me.
There is a song that describes my relationship with my boyfriend, though: "Sealed With A Kiss" by Brian Hyland. Recently my boyfriend had to move away for a job, though he really didn't want to. We try to keep in contact as much as possible, but miss being physically together, and promise to reunite whenever we can. The song describes a similar thing, where two lovers have to "say goodbye for the summer" but will "send [each other] all [their] love everyday in a letter sealed with a kiss", and "make a pledge to meet in September".
I've also discovered a few songs that describe some of my RPG characters...