You're all not doing great because it's 'forced'. Like a smoker that's convinced himself he's going to stop cold turkey by starting on XXXX date in the future. It's an addiction that you think you're going to overcome by a moment of acute yet fleeting resolve but revert back to the old ways once that feeling is gone and the reasons you're in debt in the first place comes back into play, whatever they may be. Which is why a lot of people can't make it through the day or first few days anyway.
A better way of doing it would be to calculate first what you can afford to save, then what you need to live on, then some walking-around money to fritter away. None of you are going to be able to quit cold turkey. It's going to take some time to unlearn those habits.
So for arguments sake and to keep the maths simple, you earn £100 a month.
£20 you save
£40 you live of
£20 goes on debt (if you have)
£20 goes on fritter money. Split that into daily amounts evenly and that's what you have to spend
Now you can have your No Spend day or NSW or whatever you want to call it. If you fail, just ensure you don't spend more than your daily fritter budget. If you managed to succeed, you've increased your daily limit by a small amount across the board. The more you succeed, the more that amount compounds on itself. So the main thing to take away is not so much the failure of the NSD or NSW, but ensuring that you don't breach that daily limited if you do fail.
Target yourself on increasing that overall daily spend allowance by achieving your NSD/W - not just having a NSD/W for the hell of it without integrating it into an overall financial plan. Most will end up the same position they're in, year after year. It's not unlike a yo-yo diet effect.
Anyway, good luck with the targets and all that :)