Why I feel guilty about buying nice things

Today I needed to find some new shoes, as most of my current ones are too worn out for my commute or walking around the city. I also needed to get some shoes for outdoor activities like long walks since I don't own any. What's making the shopping difficult is my constant feeling of needing to find the absolute best deal. I can't just go to a store and buy the pair I like most, even though I'm financially well-off. Instead, I try to compare every single option and end up getting exhausted by the whole process. I think it's because when I was a teenager, I had to manage buying all my own things due to neglect (not because we didn't have money), which made me overly aware and responsible for my spending.