How do you know when a project is finished?
You do get an excited rush when the first draft is complete, and it's easy to fool yourself that's the work done. But unless you are a prodigy it probably isn't. I put mine away for a while and write something else then go back for another look - it can be very painful to realise it isn't as good as you remember, although sometimes it can be encouraging when it's better than you remember. So then I have another go at it and put it aside again. You can repeat that process until:
a) you go mad or
b) you get up the courage to get some feedback - a crit group is your best bet
Then it's more revisions until you reach the stage that your eyes bleed every time you try to read it, which is nature's way of telling you to:
a) burn it and bury the ashes in consecrated ground,
b) give it up and start again or
c) send it out
Even then it probably isn't finished as agents/editors will more than likely demand more changes.
Good thing you love writing, eh? :)