It's by the Postitguy - someone who leaves these yellow sticky notes in public places all over Singapore, left to their fate, to be found and perhaps enjoyed. Postitguy has a blog: thingsweforget, where this and other gems of wisdom can be found and enjoyed.
This is how I want to live my life! Thank you Postitguy :)
Update: Postitguy has another blog: The Plan Today, which is where the above note can be found.