Themes
In case I forget to tell you later, I had a really good time tonight.
— Vivian ‧ Pretty Woman

Behind the line May contain spoilers.
Our reading
An editorial interpretation.
The speaker expresses appreciation now rather than risk leaving it unsaid later. The small qualification makes the compliment feel spontaneous and direct. It acknowledges an enjoyable evening without a grand declaration, placing the emphasis on making sure the other person actually hears the thanks.
Context reviewed