Never say to yourself "I don't want to fail"; instead say "I want to be successful." This advice comes from addicted2success.com. Why? Because our brain cannot compute all possibilities; therefore, it focuses on the input you have provided. In the first statement above, this is failure. In other words, you are focusing on the very thing you most want to avoid. That is not good.
Change what you tell yourself
When you desperately want to focus on anything other than one specific thing, the concept of infinity minus one is just too much for your brain to handle. This means that by telling yourself not to think of something, you’re actually setting yourself up for precisely that. By focusing on failure, you directly undermine your own success. Your mind will be tied to messing up and looking like an idiot.
So you should choose instead to think of something you really want. It is much better to be specific than abstract. If you say “I don’t want this or that” all the time, you are constantly thinking about all the things you don’t want. And eventually these are exactly the things you will end up with.
So change your inner monologue to “I want”. Think about all the specific things you wish to achieve. That way you will be much better suited for actually experiencing and enjoying them.
Let’s try it
Don’t think of a purple elephant. Now, did you just think of a purple elephant? Did you envisage one? You did, right? Even though you were not supposed to think of it … and that's how it is with the mind all the time.
-jk-