Once it happens....

"I came to Casablanca for the waters."
Or so she told me, once upon a dream;
I knew they didn't have such in Morocco,
But still I couldn't figure out her scheme.
The lady wasn't quite what I expected,
If I'd expected anything at all —
But let that pass. I don't need expectations.
I only wish I hadn't built that wall.

They say that once it happens, you will know it,
But somewhere down the road, I went astray;
I never could believe that she could love me,
And now I can't believe she's gone away.

She said, "You do know how to whistle, don't you?"
I thought it couldn't hurt to play her game,
And though I really didn't have to whistle,
I know now that I blew it just the same.
Did I say "game"? Oh please, say that I didn't;
Don't let me get away with such a phrase.
For it was I, not she, who did the playing,
And I who must remain within this maze.

They say that once it happens, it comes easy,
And somehow every heart will find its way.
But looking to the future brings me sorrow,
For I still haven't dealt with yesterday.

"It mean