The melody is rather melancholic, but as mentioned earlier, the song is not one-sided, and the chorus points to love as one of the constants we'd rather not change. But how do we know the message isn't so straightforward?
We know from the line "because the sky is blue, it makes me cry. The repeated emphasis on causality provided by the repetition of the title cements this idea.
The first indication of this is the airiness of the vocals, combined with the specific placement of the word 'because' so that the phrases tie in to each other, i. John was heavily influenced by her at the time.
This song is about the fact that "there is nothing new under the Sun," and a person coming to terms with it. So Lennon, McCartney and Harrison sang the three-part harmony live, then overdubbed it twice.
McCartney assumed that Ono also had a hand in crafting the song's lyrics. But the resulting song was stunning: a gorgeous, richly layered daydream that McCartney and Harrison both said was their favorite track on Abbey Road.
This approach took extensive rehearsal, and more than five hours of extremely focused recording, to capture correctly.