Don't panic, just start afresh. The first week is so hard, try to find the strength to push through! You can do it, it's only a measly little week and I promise it gets easier to deal with.
Check out some diaries, you will see that you're not alone, don't make this the excuse to fall off completely, don't regret not giving this your all. You will get literally tonnes of support here, stick with us and get that determination back! Good luck xxx