Most of you would have heard of it that if you ask mind not to think about monkeys for sometime, then mind only thinks about monkeys. This is the nature of the mind. It does not understand "No". What your think or say it understands that you want it.
So, the lesson is simple. Think and say what you want. Your mind will understand clearly what you want and it will find out the ways to achieve it. This is the reason why few people, those who are very focused on something mostly get it. They never become total failure. If you doubt your own desires and wants, then you yourself are creating roadblocks on the way of your success.
But the question is then why it is so difficult? It is because you have got a habit of thinking and talking in terms of negative statements. Like instead of saying " I am not doing something" , say " I have to do it". It is more of a habit related to what you say day in and out within our family.
Just changing on what you say, you can bring a huge shift in the way your mind works for you. Just do it and get the amazing results. So only think what you want!