Flow is my absolute favorite thing. It used to be SO easy for me as a child.
I rarely manage to sit and work uninterruptedly nowadays... but when I do, suddenly 5 hours have passed and they felt like minutes.
Gratitude on the other hand is probably my weakest one, I'm pretty cranky generally. :D I have tried it before but experienced the exact issue you quoted. Post-it notes being all colorful and the like. So I dismissed it at that time. Maybe I'll give it another shot!