Your results in life are predicated by the activities you habitually perform, and those activities in turn are driven by your beliefs. Something that many people miss, however, is that attempting to improve your outcome isn't as simple as changing your behavior, because if your behavior isn't in sync with your beliefs, it won't be sustainable. If your goal is really permanent change, then what you really must do is to change your underlying beliefs. Looking at it in a different way, your beliefs are like the software program that runs, usually unseen, beneath the surface of your behaviors. This is why it's commonly said that you can determine a person's values by his actions – if your behaviors aren't congruent with your values, they won't last for very long.
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With this in mind, it's a valuable exercise to identify and evaluate your beliefs about training and nutrition to make sure you're running the best possible software. Are your beliefs productive? Are they rational? Do they spur you to positive outcomes? Furthermore, do you hold the same beliefs today as you did say, 10 years ago? If not, you either had it all mastered then, or (and this is far more likely), you haven't grown much over that time.
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Incidentally, your personal growth occurs in direct proportion to your willingness to expose yourself to, and be open to, ideas that conflict with the ones you presently hold. Of course, it's much more comfortable to surround yourself with people that agree with your view of life, but there's also no faster way to put the brakes on your personal growth.
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Make a mental list of beliefs that you used to hold, and contrast them with your current views on the same subjects. Considering this list, have you grown over the years, and are your outcomes any better? It wouldn't hurt to assess them.