Quoted from Barry Miles' Many Years From Now:
“One of the holidays we went on, again with Ringo and Maureen, was on a yacht in the Bahamas, the Happy Days. I remember writing THINGS WE SAID TODAY in one of the cabins below deck one afternoon on my acoustic guitar. I got away from the main party but it was a bit queasy downstairs; you could smell the oil and the boat was rocking a bit and I'm not the best sailor in the world, so I wrote a little bit of it downstairs and then the rest of it on the back deck where you couldn't smell the engine. I don't know why the engine was on, I suppose we were moving.”
Written in May 1964 entirely by Paul, the lyrics to this song, in which a boy affirms his love for his girl even though she is far away, reflect the situation in which Paul and Jane found themselves - each with careers that entailed frequent periods of separation. Rather than translate personal experience into a confessional as John Lennon often did, Paul usually preferred to introduce ambiguity, to distance himself and make the song into a universal experience that others could relate to more directly.
Paul: “I wrote THINGS WE SAID TODAY on acoustic. It was a slightly nostalgic thing already, a future nostalgia: we'll remember the things we said today, some time in the future, so the song projects itself into the future and then is nostalgic about the moment we're living in now, which is quite a good trick. It has interesting chords. It goes C, F, which is all normal, then the normal thing might be to go to F minor, but to go to the B flat was quite good. It was a sophisticated little tune.”