It's tough to stay motivated enough to see the product through to market. I look at my phone full of half completed apps, and it makes me sad.
I guess one of the reasons I don't continue is because it's such a pain to develop on my my computer. It has low ram so Eclipse crashes all the time, also I always have to futz with adb to get it to see my phone, don't even think about running the emulator -- that makes my computer go OOM everytime.
I will be getting a new computer soon and maybe then I'll be able to develop more -- I even have some more ideas of what to make. You'll hear more about those later.