I'm trying to find something of value here. The best I can muster is that Truffaut wanted to make a movie as tedious, painful, puerile, annoying, illogical, and brainless as the experience of being in love. If that was his goal, then he succeeded, but the solution to his exercise is really a drag to watch.
There is one scene that screams for a spoof: Belmondo compares the features of Deneuve's face to the features in a landscape . All I could think the whole time was "glacier," "ice floe," "two lonely fishermen wearing Army surplus on a frozen lake in Minnesota."
The only other point of interest was the resurrection of Buffoon's theory of climatic determinism. The tropics are presented as paradise, and things get progressively worse as they get colder, hell being Calvinist French Switzerland. That was kind of funny.