Belying the optimistic lyric ("Baby, I feel good, from the moment I arise..."), this song was written by Kinks lead singer Ray Davies when he was going through a very difficult time.
The Kinks were on the rise, with a run of hits starting with "You Really Got Me" in 1964. The band couldn't enjoy it, however, because they were pressured into a rigorous cycle of touring, recording and promotion that put enormous strain on the group. Davies was married and hardly able to enjoy the benefits of his stardom; in May 1965 he had his first child, a daughter named Louisa. With the strains of fatherhood now upon him as well, he sunk into a depression, but was still expected to write some hits. After a few days off, he came back to work determined to make everyone think he was A-OK, so he wrote this chipper song, which he later explained was a total lie.