Have you ever heard of the Law of Attraction? You might not believe it but a positive attitude may help you finish your next project. Being optimistic about your capabilities will give you drive and inspire you to work hard, even when you experience failure. On the other hand repeating “it will never work” over and over again is probably not doing you any favours.
Isaac B. Singer (Nobel prize winner) had a similar theory,
“If you keep saying things are going to be bad, you have a chance of being a prophet.”