I write down what I want to achieve, by when & how I am going to do it. I write down excuses (internal & external in my control & external out of my control) I'd find to not eat well & not exercise. I set appointments in my diary when I am going to exercise and I meal plan weekly.
I am currently following the Michelle Bridges 12WBT, so that is where I find my drive comes from. Plus I went out last night and saw people whom I haven't seen for probably nearly 12 months. In that time I have lost nearly 15kgs & that is driving me to lose more atm.