“I can’t diet anymore! I’ll never lose weight!” Wait, what? No, of course you won’t lose weight with that mentality.
Having a positive mentality is crucial to accomplishing goals. Giving yourself trust and confidence boosts your morale and drive. High morale and lots of drive puts your body in a state of supernatural feeling; you feel like any obstacle is part of the journey to success, not something that will prevent you from success. When you feel great, you will become great.
Adversely, having a negative mentality accomplishes nothing. When you become pessimistic, you tell your brain that no matter how hard you try, you won’t accomplish what you set out for. Your body becomes unmotivated and unwilling to continue on, as it feels like there’s no purpose or reason to try. It asks itself, “Why try when I know I’m going to fail?” Likewise, Hamlet has a very pessimistic outlook on life after the death of his father to the point where he contemplates suicide.