I do a Weekly Review, but I do not plan my week the way I plan my day. When I plan my day, I have a list of items that I am seriously committed to accomplishing that day. If I don't complete every single item, I view myself as having failed in an important way. My paradigm for this is having a doctor's appointment. I tell the doctor's office that I will be there tomorrow at 10 AM. I view this as a serious commitment. It's true that I might get stuck in traffic; I might forget; I might have a family emergency; my workplace might burn down. But, generally speaking, come hell or high water, I expect to be in the doctor's office tomorrow at 10 AM.
My daily plan is a day-specific appointment with myself.
I do my GTD Weekly Review, but it is much less rigid. I might write down a few projects for which I want to get some actions completed during the week, but I don't have that same "come hell or high water" attitude. A week is a long time and I suppose (I haven't actually tried to do it yet) it's too hard for me to plan with any accuracy everything I will get done in the next seven days.
When I formulate my daily plan, I might phrase the items as actions or as projects. A project is a state of affairs "Salary analysis completed." I know that I can go to my trusted system to find the NA for that project. And I can then look at my project plan or use common sense to figure out the subsequent actions required to get the project done. Other items on my daily plan are NAs. Either they are unattached to a larger project, or they are attached to projects but I don't expect to have that project completed today.
If there is some urgent, uplanned situation that throws off my daily plan today, so be it. I won't be able to give myself credit for marking off everything from today's list. But tomorrow is another day, another chance to get every item on my list done.