You could start it sooner - it might be therapeutic to write down what has happened to make you want this surgery, how you feel about yourself now and how you feel about the upcoming op. It's obviously not a fanciful notion on your part.
And remember to take photos of yourself so you can see the changes. Once a month stand in front of a door or upright freezer for the photo for perspective and it will surely help you feel good about yourself. Looking at yourself in the mirror every day will not help you see how much you are changing.
I admire you for having the guts to actually do it.