To me, this song is about surrendering to love.
Champagne is an interesting analogy, because it's a high-class drink enjoyed by the wealthy, but it also gives you an instant buzz and lets you release inhibitions in a spirit of celebration.
She's saying that she is always thinking and dreaming about
him, and gives into his advances (and into her feelings for him) all the time because his love is so complete and delicious that literally, the whole world fades away:
"...leave it all tonight," and ""When there's nothing left except you and this..."
I think it's a beautiful song, and speaks to the contentment of feeling so completely free with someone that you literally fall asleep counting his kisses.