It is an accepted risk. Unless you are independently wealthy, you must sometimes make choices in life. If you want to buy B, you may have to sell A.
If you already own X number of guns (and X may be 3, or 10, or 20) then you may not have the funds for X+1. So you sell an existing one to fund a new one. To be clear...your choices are a) selling something you own, or b) keeping what you own, and never experiencing something that you would like to own.
To many of us, that is an easy choice...especially if we own 3, 10 or 20....if there is something I really want, I don't have too much trouble figuring out which one I am not getting much use from.
In this manner, I have managed to own about 100 different guns in the last 20 years...ten at a time. Similarly, I have managed to own 80+ motorcycles in my life (so far), two, or three, or four at a time.
Would I like to own all of them at once? Sure. But that would never have happened. Am I happy having owned a bunch of them for a limited time? Absolutely...because I have kept (or bought another example of) the ones that I liked the best.
And if I hadn't owned them all, how would I know which ones I liked the best?