Without stretching my brain for more than a second -- there must be hundreds of them ("Let's Spend The Night Together" by the Stones being one) -- two of the more optimistic songs I can think of offhand are "Hey Jude" by The Beatles and "Ooh Child" by The Five Stairsteps (written by a guy named Stan Vincent, a pop producer of whom I know very little). Boiled down the latter has few lyrics:
Ooh child things are gonna get easier
Ooh child things'll get brighter
Someday we'll get it together and we'll get it undone
Someday when the world is much brighter
Someday we're gonna walk in the rays of a beautiful sun
Someday when the world is much lighter
Ooh child things are gonna get easier
Ooh child things'll get brighter
Right now
As in any optimistic song, epitomized the Beatles and the Beach Boys, the uplifting feel of the music plays an integral part in giving you that sense of hope. But at the same time, as illustrated by the preceding example, there must be an underlying implication of sorrow associated with the current condition to contrast with the feeling of optimism about the future. (Indeed the compelling repeated guitar lick from "Ooh Child" is tinged with bittersweetness, and the implied but unanswered question hangs in the background: What happened that must be "undone"? It doesn't matter; the healing will be accomplished in time.) You need something to triumph over -- simply being blatantly upbeat about everything all the time doesn't qualify.
Then again, who hasn't ever gone in a big way for a song that's just so poignant or melancholy, but with grace and not merely wallowing in self pity, that it makes you feel perversely wonderful by giving your soul solace? Along the lines of "Waterloo Sunset" by The Kinks for example. You just think, hey, if someone else can feel that way too, and make something beautiful out of it, then there must be hope of good in the world. But most songwriters who sit down to write a piece that's simply sad, or simply glad, usually come up with a piece of sentimental dreck. As the man is reputed to have once said, all great poetry is at root about death, even if it's ostensibly about love...
