Mostly I lose interest, cause things don't go my way or turn out the way I see in my head. I have to say at any one time or another have as many as 18 kits started, some from as far back as 20 years. But last year I did manage to finish 3 kits I started (modified) some years ago, mind you none of the three were finished the way I thought they would back then. I am also a lot older and wider sorry wiser. HaHaHa A good friend of mine does not start another kit until he finishes the one he has opened.....go figure!