It is necessary at times to spend money. I think of it like this "Take care of yourself now to save yourself from worse health problems down the road."
For example, I wore my favorite pair of leather Tevas (sandals) for 6 summers. They still looked fine. I could have kept on wearing them. But the supports inside were worn out and my feet hurt. So I finally broke down and bought some nice Chocos last year. I did find a deal on them, but I usually would never have spent so much on sandals.
My feet have been very happy since. I love them.
What is your big indulgence you can't live without?