The analogy to a carpenter earlier in this thread reminds of a few years ago when I was lucky enough to be invited to the preview of an exhibition of work by the artist David Shepherd to mark the opening of a new art gallery. Of course the man himself was there to talk about his paintings. They were wonderful - he is a suberb portrait painter - but in among them was a small oil painting of a stormy sea crashing over fractured rocks. It was quite awful, very dark and amateurish. David explained that it was his very first attempt at an oil painting and he always exhibited it to inspire new artists and show them that no-one, whatever their craft, is instantly accomplished.
I'm not suggesting that we lug our first efforts round publishers to demonstrate how we've improved since we wrote it. The reason I like the analogy is because it made me realise how we, as writers, are different. Until we get a novel/poem/short story published we, unlike carpenters and artists, can continue to polish and improve it. Personally I like editing and re-writing. If I'm stuck with the plot line or a new scene I go back to earlier ones and polish them up. That usually breaks the logjam and lets me move straight on to new sections. It works for me so, Traveller, relax in the editing room as much as you want. It is all valuable work. In answer to you last couple of points about plot - yes you do need a plot but whether you work it all out in advance down to the last detail, or let your characters direct the action as you go, is up to you. Do whatever suits you best.
Good luck,
Dee.