antonym of "spoiled"

I think deprived pretty much captures exactly this feeling.

I have been so deprived by these shoes, anything else would feel like angel wings by comparison!"

The implication here is not that the speaker has turned their adversity into a strength (such as with the use of the word hardened), or somehow overcome their disadvantage; that would imply a positive connotation. Rather, they have been “defeated” by it, and even a minor improvement over their current situation would seem grand by comparison.

Indurated:3. to inure; accustom: to indurate oneself to privation and suffering.

To be made hardy: capable of enduring fatigue, hardship, exposure, etc.; sturdy; strong otherwise known as “hard as nails” (idiom)

I like the word desensitized here.

: to cause (someone or something) to react less to or be less affected by something : to cause (someone or something) to be less sensitive

I would go with toughened in this case (or toughened up).

Spoiled in your example is equivalent to weakened, or made more sensitive to. Toughened is the opposite, less sensitive and stronger.