Even though I cannot figure out who originally said this, it inspires me daily. Whenever I think about the vagueness of the quote, I realize that it really applies to anything in life. I know that I can easily apply this mindset to any situation, especially a situation where I'm plotting to get out of it by saying "I can't."
Determination and believing you can is half the battle. I need to remind myself of this more often, which is why I have a canvas with this quote on my wall above my bed. It's the first thing I see when I wake up and the last thing I see before I go to bed.
While a simple quote obviously isn't the main reason I believe in myself, it stands as a permanent reminder. When I'm doubting myself, I just have to think about the fact that I achieve anything I want, if I really want it badly enough.
Everyone should wake up daily believing that they can achieve anything in the world. It just takes work and determination. With those two things, everything in life is possible.