Staying strong is one of the hardest things to do. First and foremost you really have to want to lose weight, that will be your biggest motivator. I also find looking at thinspiration helps a lot which is why I run this blog, and looking at and counting calories keeps me motivated because I get so disgusted at the amount of calories things have. Let me know if you have any other questions!
Also setting multiple goal weights helps because they will be closer and easier to achieve.
i want to be tiny tiny tiny