Of course there are no 100% guarantees in life, but when you have a positive mindset like the one this quote instills you’ve got a pretty good shot at getting it right. Success begins in the mind, and if you go in with a defeatist attitude you’ll surely come up short. Just think of what you could accomplish if you had the belief that you would succeed. You don’t need to be completely assured of success, it’s good to have a bit of a possibility of failure or it wouldn’t be interesting. Just go into it with the confidence that there’s a high chance of success for you.