I know it's hard, I came very close to bronzing my import dreamcast and encasing it in glass.
Seriously though what helps me is thinking about cost per hour, I can afford plenty of games but it bothers me when I feel I haven't got my monies worth out of them. For example if I only played a game for 5 hours I payed 10 bucks an hour to play that game. That's crazy and bothers me, yet I don't really care to play it more, and let's face it better and better games are coming out, the day that I keep assuming will come where I pop it in for the heck of it just won't come. So bringing that game back and in this case getting 25 dollars for it is like I only spent 25 bucks to get that five hours and in turn only spent five dollars an hour, which isn't too bad.
Or think of it this way, you might have regreted buying Farcry, but say to yourself yeah, but buying farcry got me half off SSX. so I think it's worth it. Honestly it only pays to keep your really good games. I traded in alot of stuff, but I plan on keeping Zelda: TP, Warioware, and games I bought used for cheap too I keep.
And the bottom line is lets say that day does come where for some odd reason you wake up and say, "Why did I get rid of Farcry!!!!" Then go rent it for the weekend, it would still be cheaper to rent it a few times and get rid of it then it would to just keep it.
Unless of course you have a giant basement with shelf after shelf loaded with games and you want to expand this so you can invite people over to view this master collection and laugh victoriously. HAHAHAHAHAAAAA!!!!! although it might kill the impression to mix your collection with the inferior titles.







