Day 1: Brown Rice

This is the first day. It will be very hard to adjust, because in some ways it's like a fast. Without the excess sugars, calories, dairy, etc. your body will be surprised. Your mental state may be affected, so it's probably best to start this on a day with as few stressful events happening as possible.
It will help to cook a big pot of rice and put it into smaller containers to reheat throughout the day. The idea is to eat as much as you want. But of course, you won't necessarily crave lots and lots of rice so you're unlikely to overeat. Sometimes you may just eat it cold if you're looking for convenience.

When you eat your first bowl of rice, start with thanks for the fact that it's hot, and the fact that you have water, a pot and a stove/rice cooker to prepare it. Even just plain rice can be very comforting when it's warm.

As you eat the rice, take time to sense the texture in your mouth. Think about what the substance of it will contribute to your body. You will receive energy, fiber, and even a small amount of protein from this. It will be enough to sustain you for this day, even if it's not a "proper" diet. Many people in the world are eating this same meal now, but not by choice.

This food is ultimately a gift from the sun and the earth. You may have paid for the labor to plant, harvest and transport it to you. But you couldn't possibly earn the energy that it provides to you. Try to imagine the journey of sunlight energy that's made its way to you and will sustain your existence.

If you can keep some of these thoughts in mind, it will likely help to stave off feelings of deprivation. In my experience, this was definitely the hardest day, because I was confronted with an intense focus on food. But I did what I could to nudge those thoughts into ones of thankfulness, and it helped quite a bit.