Get confident. Along with thinking positive about your world, you gotta think positive about you. If you think you're incapable, it'll seriously put a damper on the amount of effort you give this task. Why would you bother doing something you don't think you can do? Exactly. You won't.
To get started, count your successes. What do you have going for you? What have you done in the past that was awesome? What resources do you have at your disposal? Think of all the things you've achieved in the past. For what reason would you not be able to achieve what you want now?! You've done similar things before.