My 2012 resolution was to attempt to avoid spending any money on Mondays. tldr: I came nowhere close to that goal but it was interesting.
In 2010, I was slightly annoyed by Amazon deciding to stop hosting WikiLeaks website so I made it a challenge to avoid buying anything off Amazon in 2011. It was difficult especially for all those little things such as odd batteries or MP3 albums from obscure music groups. This year I decided to step up the challenge, instead of trying to avoid spending any money on Amazon - I would try to avoid spending any money at all on Mondays.
My only rule was no spending physical money in the form of cash or card and no spending money online. I allowed Monday holidays and Mondays I was on a work trip or vacation day to be exempted. The hours were from 12 am Monday morning until midnight Monday night.
I would estimate that I was successful in about ¾ weeks per month on average and probably 40 Mondays for the entire year.
The two biggest things I noticed:
This did not really affect my spending on larger items. I noticed that if it was something that I wanted that was more substantial than just coffee I would have no qualms waiting a day to purchase it. Most of the purchases I did not make were for things I could spend less on such as trips to the coffee shop.
I felt more focused on Mondays. With no option to take a break and walk to the coffee shop or wonder about where to eat lunch, I was able to keep my head down and get some good work done.
Looking ahead, I will continue to avoid spending money on Mondays because I find it to be an interesting challenge and anything that can help me stay focused is highly welcome in my life.