Question: I'm looking for an antonym of the word *spoiled*.

The sense of *spoiled* I have in mind is a positive one: "I've become spoiled by these comfy shoes."

I'm looking for a word or short phrase to say: "I've become *antispoiled* by these horrible shoes and now any other pair would be comfortable."

The closest phrase that I'm aware of is *to have one's standards lowered*, which isn't quite the same thing and certainly isn't very pithy.

Answer: 
You could say settled for less comfortable shoes.

settle for something
to agree to or accept something, although it is not exactly what you want
"These horrible shoes have made me *{less {fussy / choosy / discriminating}} / {more {easygoing / tolerant}},* and now any other pair would be comfortable."