I feel a lot of what the OP and others have posted here; especially the fixing stuff right before you sell it that you've put off for years. Worst habit ever and I'm totally guilty!
Living in a condo the past couple of years with no storage space has sorta constrained me, but I still have two project cars down at a friend's shop. Now I just built a huge shop of my own. I'm not even working in it yet until the house is done and we have power in the shop -- yet I'm already trying to justify plopping a couple of cars over there because we have tons of room now.
I'm trying to stick to a rule that I only work on one car at a time. It's the only thing that has even kinda sorta worked for me.