Manifesting isn't so much about thinking as it is feeling. It's the vibration that you are putting out there. You can think positive thoughts, but if you have strong feelings of worry or anxiety over your situation, then you will keep living your current situation. It can be quite useful to really look at what you want to change and then pick out any good aspects you can find about it. Doing this will make the situation seem a bit better and it will help you to move your feelings to a more positive place.