The Strokes - Last Night Lyrics Meaning

It's about his loneliness.
He's describing the angst of a young man born into a life that noone understands, and they don't understand becuase he can't tell them.
He's caught in a world of illusion, and feels he's been born into something he won't ever understand.
It's also a parallel for the existential human condition. It has a double meaning, but he thinks his meaning leaves him in a worse position - and yet ironically better as it is a point of some privilege. That is not true though.
He feel that the people, his girlfriends, his partner, his extra terrestrial friends - virtually everyone (except his parents it seems) don't understand.
But she understands. She actuallly understands the essence, which is love - she can't shut her out just becuase she doesn't understand. She is teaching him that love heals all wounds and brings down all lines of demarcation. That's when he turns around. Love is his saviour.
In that love he can find that it doesn't matter, because humanity is choosing this. It is humanity that choose the sleep, not him, not his family, and not his extra terrestrial friends either.
We all choose the great sleep. It is the mass consciousness that is the master puppeteer - the privileged few were put in that place by them.
They don't understand becuase they don't want to, they don't want to understand the truth becuase taking responsibility for who we are has not been what they wanted.
Once he realised that, he'll understand, and he'll know it's ok - understanding is both underrated and overrated - that's just duality ;)