"Don't spend any money today."
If you can avoid it, don't spend it. Sure, you have to eat and maybe even take public transport to work, but other than necessity, do NOT spend any cash today. Either have someone cover you and pay them back tomorrow or find a free alternative to what you need.
I can do this. My metrocard was prepaid so I technically spent that money a week ago, not today. And since John is taking us to dinner tonight, I won't have to spend later either. Now to see about lunch... We have free ramen in the breakroom which breaks my diet, but won't kill me. And the watercooler plus my tea packets equals free refreshment. YAY!
Goodluck to the rest of you! Pinch some pennies today and use them to spoil yourself another day.