44 Man,
Like you, I could never afford to keep all the guns I've owned through the years. A couple I regret losing are my NIB 3rd generation Colt SA in .45 Colt. Purchased in the late 70's for $475.00, at a local TG&Y of all places, with money borrowed from my brother. I was raising a young family at the time and couldn't justify keeping badly needed funds tied up in a pistol I seldom was able to shoot. Sold it in the mid-80's for $600.00 and thought I did well.
I had a Colt New Frontier .22 lr, purchased new in the early 70's that was dearly loved. Someone stole it out of my car in the mid-80's. These guns are now way too expensive on the second hand market for me to replace it.
One I wish I could have bought was a 2nd generation Colt SA, in .45 Colt , with stag grips, that I spied at a gun show in the mid-60's. Priced at $90.00, I had the funds but was too young to legally purchase it on my own. The adult that accompanied me to the show didn't like the dealer and vowed to find a similar deal elsewhere. Alas, it never happened.
But even with these losses, I now own more firearms than I ever dreamed possible "back in the day". Ours is a fun hobby and, to my way of thinking at least, selling and trading are part of the excitement.
Cleburne