Say Yes

The morning after refers to the morning after a one night stand. In the morning after a one night stand, the reality of where she is tends to hit, and the girl leaves.

There's a turning point in relationships when you see the reality of what the other person is like, and you leave or stay.

He's laying in bed, happy, reflecting.

"it's always been wait and see
a happy day and then you pay
and feel like shit the morning after"

For him, it's always been a wait until that point (although he was happy before it hit), but then he paid for having a relationship when they got to that point (and she left).

"now I feel changed ... down I'm standing up the morning after"

Now that she's remained with him in "the morning after", he's happy.

"situations get fucked up and turned around sooner or later"

His relationships always get fucked up at some point (at that turning point)..

"and i could be another fool or an exception to the rule"

in this particular relationship, he was just waiting which one of the two outcomes it would be: him being a fool again for trying, or the exception to his feeling that this would always happen...

"you tell me the morning after"

it all depended on what she would do the morning after.

"crooked spin can't come to rest I'm damaged bad at best she'll decide what she wants"

It's like he's in a constant car crash, he's in bad shape, and now she'll decide what she wants.

"I'll probably be the last to know no one says until it shows see how it is"

He'll be the last to know if she chose to leave him, nobody says anything until it all becomes clear to him, that's how it is.

"they want you or they don't say yes"

this part is particularity good: 'they want you or they dont' 'they want you or they say no' 'say yes' (want me)

and now, back to the beginning:

"I'm in love with the world through the eyes of a girl who's still around the morning after"

She stayed, and he's in love with everything (enjoys life) through the fact that she wants him.

"we(/they) broke up a month ago n' I grew up I didn't know I'd be around the morning after"

In the live kcrw recording, he sings "we". In the soundtrack he sings "they". The Ben Folds cover sings "meh" (likely because he too doesn't know which it is).

if it's "they": She was with someone, they broke up a month ago and that's how long our couple have been together... all the while, and all his life, he didn't know if (he'd?) be around the morning after. ("I'd be" perhaps because if she isn't in the relationship neither is he, or he becomes after a breakup as disillusioned with a girl as she was with him)

if it's "we": they broke up a month ago, he grew up during that time, realizing that he's "still there the morning after". He goes back, and she's still with him the morning after. (After she realizes what kind of person he is, breaking up with her and all). (as juicyclad said, but different ending)