I never, ever feel guilty about returning anything. I am a plus size and most stores only carry my size online. They leave me no choice but to buy things I am not sure will work, so I don't feel guilty when it doesn't.
I worked in retail for a few years too, and my experience matches Christine's. Plus, once I saw how many people returned clothes, I got over any hangups I had about it. When the store was closing near the end, there was a tsunami of returns that people had been hanging onto in their closets and they had to make a decision before we stopped accepting them. There were days when we were just glad we had made more in sales than we had in returns, LOL!