Just a quick explanatory post about the 3 priorities as this is something new.
The general idea is to have a list of things you want to work on until Christmas (and hopefully afterwards). In general people have about 10 items on their list (list ideas can be found on the prep thread linked above).
Say for example I have 10 items on my list, exercise, drink more water, no Coke, floss, vitamin, wash face every night, do nails, hair removal etc.
For the first 3 weeks (because apparently it takes 21 days to form a habit) no matter what else goes wrong or how well everything goes the 3 things I NEED to do are floss, vitamin & wash face.
If you only want 3 items on your list, that's fine too but please don't feel restricted to 3. Or in 3 weeks pick another 3.