The song is about someone facing something so beautiful that it is not clear what to do with this beauty. It takes days or weeks to absorb it and get back on the regular track. 
This can be a great book (i.e. "For Whom the Bell Tolls" by Hemingway), a soulful movie (like "Knockin’ On Heaven’s Door") or a painting like "Ship on Stormy Seas" 1858 by Aivazovsky or nails flying in the deserted landscapes of Dali.
It can be someone you know so well who opens up from a completely unexpected yet stunning side. Or it can be a beautiful lady in the red dress that is crossing paths with you on your routine morning walk.
With all of these things "the moment" is "passing" and there is no way to feel this first impulse again but your mind is refusing to believe and it keeps "thinking of lady in red" ...

Lady In Red

Sunny Day

Ready to Go

Art Police - the band playing its own honest material in the rock genre.