A positive thinker:
Sees the invisible,
Feels the intangible,
And achieves the impossible.

There are things that seem invisible and intangible that can actually be seen and understood with just a change in our frame of mind. 

What the mind does not know, the eyes will not see. A negative person will miss something that is right before his eyes and miss seeing the possible outcome as a result. Knowledge and a positive attitude will open your eyes to numerous possibilities that would otherwise seem to be impossible. 

With knowledge and an open mind, even things that are intangible can be seen to exist. When you know that things exist, the ability to use them to achieve goals is much easier. You know how to optimise your efforts and where to direct your energy. You learn to ignore discouragement and focus on possibilities rather than impossibilities. 

Armed with the above 2 tools, you can achieve things that you may have labelled as impossible! You can prove to others that impossible is nothing. With these tools, you will also find that true impossibility is a much smaller problem than what you think it could be. There will still be the occasional failure and the occasional inability to achieve some things. But these will happen only after you have conquered and realised all your strengths and powers. Yes, there  are limits to what you can do, but that are few and far between in ones life. Even failing after giving it your best often give you lessons and insights that will make you better and not bitter.