opti fast

has anyone else needed to do the opti fast diet prior to their surgery? my date is two weeks from monday so i have to begin the shakes this upcoming monday and i'm a little terrified. i want this more than anything but i'm scared i don't have the will power to stick to only those shakes for two weeks and as if that isn't enough, i also need to have lost 17 lbs by january 14th. does anyone have any advice on how to deal with just these shakes?