Someone looks the speaker in the eye and says, twice over, that they don't want to fall in love with them. The speaker's only response is to smile. That's the whole scene, and the poem leaves everything else unsaid.
The smile is the interesting part. It could be polite acceptance, or a way of hiding hurt, or a kind of knowing amusement. The note under the title, "he was lying," points to the last one. The speaker seems to hear the denial as a sign of the opposite: if he has to say it so firmly, and repeat it, perhaps he is already falling. (Note that "liked" in the first line is probably a typo for "looked.")
The mood is quiet and a little tense. The lines are short and plain, and the pause before the final line makes the smile feel loaded. It reads as someone holding a private certainty while the other person tries to talk themselves out of their feelings.