Life has a funny way of throwing you curve balls during the writing process. I suppose it's all really a matter of how you deal with them that matters. If you can take that apparent hindrance, regardless of what form it takes, and make something positive out of it, that's what makes the difference. In screenwriting it's called a test of character.
There's plenty of reasons to turn tail and give up in this town, especially in this profession. I have the fortunate nature of personality that includes an overhwelmingly optimistic outlook on everything (it can often be a curse). But if it wasn't for this and the love and support of family and friends, I would have turned tail by now. Then there's that whole "talent" thing - but honestly who really cares about that.