Monday's Riddle! A Sour, Green Wave

Hello Riddlers and Welcome to Monday! In Fiji, it's already Tuesday- I wish I could trade places with someone there so the weekend would be here sooner. Can you guess the theme this week? ; ) ~ F

When there's a wanton purpose you've seen, I'm the tide that turns you green. I'm a fixated wave that inspires a glower or an internal soup that's always sour. Should desire come knocking when it's fortune you're sewing, you'll realize soon that I'm not much worth knowing. For, I should be lost whenever I'm found or I'll get your mind going like a merry-go-round. 

What am I?

I gave you a clue!
FEAR NOT THE UNEXPECTED