Much like you. My poor choice was selling a PRISTINE and VERY correct WWII Winchester M-1 carbine that I had in the late 80's. Why I sold it...for the life of me I do not remember what other gun I thought I just HAD to have? Being young and dumb and having a wife and two small children to feed at the time is my only excuse.
Yep, that's why I included it in here. I was around 22. Didn't make the connection that I needed more powerful ammo. 9mm didn't have much in the line of carry ammo then either (being nearly 30 years ago). I always wanted one, so I got it. Paid out the rear for an extra mag as well (M13).
Year or so after I got rid of it a buddy and I started toying around with reloading. That was probably when the lightbulb turned on. I stopped buying other people's reloads... for a while at least.
I once had a an FN-49, in 8mm Mauser, Sold the gun, and the next week saw in Shotgun News, FN-49 firing pins $5......aaaarrrrgggghhhh!!!! Now as to deals not made, passed up buying a full auto Mac-11, in 9mm for $400, plus $200 transfer tax. I had orders to Germany, and needless to say, full auto wasn't legal to transport over seas, and you can't just store it with relatives......