I perform magic and miracles, greatness flows through me.

 

When things are going your way and you are feeling good, there's no need for positivity because you feel like you can do anything. A good trick is to get into that state when things are not going your way, when you feel like crap and it's not firing on all cylinders. That's when you really need to dig into that well of wellness inside you and let it come out. A good way to do so is to associate a mantra or saying which turns seemingly negative states of mind into positive ones.
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So you can state to yourself that you shine no matter what and you are always able to be in the zone regardless of what is happening. You can state:

If there is fear, I perform magic and miracles, greatness flows through me.

If there is doubt, I perform magic and miracles, greatness flows through me.

If there is a feeling of humiliation or anger or pain, I perform magic and miracles, greatness flows through me.

If there is a feeling of intimidation, anxiety, nervousness, threat, that is when I shine brightest, and when I perform magic and miracles, greatness flows through me.

I take a deep breath and I perform magic and miracles, greatness flows through me.

No matter what,
I perform magic and miracles, greatness flows through me.
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With continual association of these mental and emotional states with this positivity, it subconsciously takes over you mind and you act in accordance to this empowering belief. It's deeply lodged into your unconscious mind and you can't help but to operate under this new positive software running in your head.