Queens of the Stone Age

I would say it's about a guy in what he believes to be unrequited love with someone who actually feels the same, and getting that sudden smack to the head when he realises.

I suspect that, from the first verse ("We get some rules to follow") the girl might already be in a relationship with someone else... you have to follow "the rules" and stand off if she's already taken, but the guy wishes that it weren't so. A bitter pill to swallow.

Then there's the "journey through the desert/of the mind, with no hope"... anyone who's been in the situation of being in love without being able to express it knows that seemingly-endless and utterly hopeless trudge through life. And by the end of teh second verse, he's at the stage where it all comes to a head, and he "come[s] undone"... he's almost ready to give up, "pleasantly caving in" as it's almost a relief to accept the total abandonment of painful hope.

And then, in the last verse - just when he thinks things can't get any worse - we get what the chorus has been hinting at throughout... "I realise you're mine"; suddenly his jaw drops and reality turns sideways as he suddenly gets that the girl wanted him all along - maybe she went with whoever else just to reverse-psychologise him, or maybe she was just tired of waiting alone and found a 'silver medal' guy, because the one the girl really wanted all along was too wrapped up in his own lack of self-belief to believe he even had a shot. He just had to come round to it in his own time.