When I browsed for optimistic songs, I came upon Move On Up by Curtis Mayfield and loved what I heard. The song written by the singer himself was taken from track 5 of his debut album in 1970 called Curtis (track samples and review for special edition).
Sorry for the poor visual quality, but I couldn't find a better video. If you come on a greater version, please let me know. Well... actually I found a few videos with better visuals, but I couldn't hear the awesome sound of instruments and see these talented children play music. So, I decided to go for this one. Just listen to the music and lyrics to feel soul all the way. Have an uplifting week, everyone.