This has certainly been true in my life! Perfect example: Writing a doctoral dissertation. When the times get tough (and they definitely do!) I remind myself that "I have this!" Another example: When I've had to balance a lot going on at once, and I wonder how I'll get it all done, I remind myself "I can do this, I have before, I will again!" When have you created outcomes with positive (or negative) thinking?
Write something about yourself. No need to be fancy, just an overview.