My essential rules of finishing a piece of creative work:

1. Know where you're going before you start

      - A sure fire way to lose interest or motivation is to start something which you ultimately don't know how is going to end.

      - Get the main idea down and then layout the entire structure as soon as possible, even if it's rubbish. It's much easier to work when you can physically see or hear an end.

2. Too much work in the details makes you lose sight of the piece as a whole

   - It's very easy to get lost in how particular things should be phrased, what words/sounds to use, how the tiniest detail should sit. It's all well and good until you come out of that and realise you've kind of lost the overall picture.  

3. Don't expect to produce anything good for at least the first 45 minutes to an hour

  - This is the time most people give up on an idea but this a crucial time. For me, this is just when I haven't really produced anything good yet but I'm just about in the zone. Don't stop now.  

4. Enjoy what you're doing.

  - Cliche but simple really. Sometimes you feel that urge but there's no point in pushing through if you're not enjoying yourself. Sometimes it's hard, but it should never be laborious.