I screwed up

Long story short, my fiancé and I are getting ready to move. I’ve been packing and selling things we don’t need anymore. I sold an item that we agreed we would sell for a specific price a little cheaper than we agreed. He got SO upset. It was something he worked hard for and felt disrespected that I didn’t do what we talked about. I get where he’s coming from and I feel so bad. I’m very laid back and chill and he definitely has a tough time letting go of things or relinquishing control. Me selling this item at a cheaper price was kind of the straw that broke the camels back I guess, in a list of things that I didn’t think was a big deal, but it’s a big deal to him. I feel like a shitty partner.... I made a mistake and I know it. I just honestly figured it wouldn’t be a big deal🤷🏻‍♀️ He’s so pissed and I don’t want to be the reason he’s hurt. He had to work tonight and was so upset he didn’t even want to talk about it. Any advice from some seasoned wifeys on how to rebuild some trust and help him feel respected?

Side note (don’t know if this matters) the price difference was $10. He said it’s not the amount, it’s the fact that I didn’t follow through with what we talked about.