As others have said "planning" is definitely the key. But what is also important is acceptance that things may be more uncontrollable because your routine will be affected by others around you, ie. family, friends and so on. And if you take this into account, you shouldn't be face with an surprises.
Plan as much as you can, and what you can't plan, make the most of!!!
You can plan your meals, and your water consumption by taking stuff with you. But if you find yourself at a restaurant or someone's home, you don't have to deny yourself EVERYTHING, make healthy choices as much as possible, and if you can't, eat smaller portions (so not to offend hosts).
All the best with the first weekend!! I'm sure you will do just fine!!
Strong people don't walk away from the truth, only the excuses others try to sell them.