21 days just seemed like the sweet spot....I had heard before that you can change any habit pattern in 21 days...

and I am a big fan of the number 22....and the challenges being 21 days...makes the 22 day a real celebration.

Also 21 is a 'triple 7'...and I like numbers....and 777 is the big jackpot!

haha - just playing around with things....didn't put too much thought into it....but took note of the points I mention here....

Also by doing a challenge for a set amount of days...it's a way to create structure for yourself...and a way to document and learn from the process by having kept a log of the journey.