its a mental block as well as a logistical one. addition of features becomes tougher (not dependent on the inherent complexity of a feature) and the UI itself becomes a challenge.
I know each of us is different and so I ask you to please share some tips, if you have, as to how you deal with this.
A feature that you could whip out in an hour with an 90% chance of working bug-free now takes a day, because you need it to be 99%. It becomes easy to put things off "until you have time to do it right" - even small and easy things.
The way to combat this is to work on your environment. Build a solid staging environment. Automate some integration tests (http://fakeapp.com is awesome for this) for the must-have functionality. Work on your admin dashboard so you know the instant something goes wrong. In other words, build the tools that make your next deployment as worry free as is practical. For me, the friction and misery of the QA cycle slows down my releases until I get all this stuff right.
It's a head game. I know when to stop writing tests when I'd rather be working on the app.
also, I find that new projects start to look very appealing because of the lack of that entry barrier and lower costs of making a mistake. Then it becomes a mental barrier to focus.
It's just like cooking in a messy and crowded kitchen vs a clean and spacious one.
managing iterations, to me, is beginning to seem like a big unexplored science and art. big enough for someone to write a book about this as the central topic, I feel.