Confidence, that’s half the job. To be able to go into the last week of a project and be confident in your product is half of what you need to get the game done.
At this point in the process you should have everything programmed, all the art in the game, all the audio final, and should only have to polish. The only reason you should not be confident in your game is if you haven’t delivered on what you set out to get done, if the game isn’t what it’s supposed to be. By this point, confidence will say everything you could say about your own game.
Being able to answer the question “how do you feel about the game at this point?” with a straight face and a “great, we’re nearly finished we just have to tweak some things” then you’re golden.