They say you have to become very optimistic to become successful and get big things in life. But sometimes people don't want to even work anymore because they think that everything will be fine. They always say "I will just do it tomorrow because I knew I can do it, there is no need to worry." They were so addicted in positive quotes, motivational movies, inspirational speakers etc. That they don't even know how to work hard anymore. All they do is dream, talk about their dreams, motivate people and do nothing in their lives. The funny thing is they don't noticed themselves not progressing anymore because just like I said... they were too positive.
Sometimes being optimistic will make you weak. You will get soft. For example a fighter will not train so hard because he knew he can beat his opponent. He was so optimistic that everything will be fine and he will become victorious in the end. He is not anticipating a big challenge ahead of them that is why he falls short in the end. All he thinks is he will dominate his opponent and raise his hand after the fight, he is not anticipating adversity. So when the going gets tough... he was stunned, he can't do anything, he was not prepared because all of his training days were taken for granted.
You have to become realistic in life, it is not an easy merry-go-round thing that will give you anything you want if you become optimistic and have a positive outlook. You need to work hard and be prepared for any adversity that may come. You can't be dreaming about winning without working.
Being optimistic without working hard is like wishing for a pot of gold to fall from the sky. Yes you are being positive but you are not realistic. And that is what make things impossible... wishing for it without suffering for it. It is ok to become very optimistic but you also have to become realistic.