I am not much into psychology.

You either want to be rid of the gun or you don't. If you do, take a guess at the best way to get the best dollar on your sale and get to it. If you don't then I would tell myself to quit agonizing and either use it, return it to its original configuration if you can, store it, or give it away.
As one prone to agonizing over such decisions myself, it's probably easier to sympathize with the OP's dilemma (even though we may still be missing some very critical facts here). Since I joined this forum, I've taken note of the number of members who claim to think of their guns primarily (or solely) as simple "tools", no more, no less. Kinda like a hammer or a screwdriver or a toaster, only a bit more expensive and noisy.

Yes, they are tools for sure, but I don't think we would all be here participating in this forum if they were really no more than simple household tools or appliances.
The truth is that there is a financial/investment component, a pride component, a personal enjoyment component and much more. It's about a hobby, not just a tool. The decision to sell something that you've put a lot of yourself into (and/or money into) is sometimes less easy for the "non-tool/appliance" folks among us.
Perhaps like a stock or other investment gone bad, maybe the OP cannot accept the decision to sell as being prudent? To do so is to solidify and make permanent your loss and have to admit your mistake.
On the other hand, further losses are unlikely... so keeping the bad investment could be a constant reminder to one's self to not make the same mistake again.

And, after all, it's not really an awful lot of money in this case.

Chump change, really.
I think we need to know more about the gun itself. Something tells me there is more to this story than just finances and safe space.
