If you are female, and had been dreaming of being a ballerina, it can mean you desire to be someone better.
If you are a ballerina and dream of yourself as one, it can mean your dreams are simply continuing the same theme from your waking reality.
If you are female and dreamed of seeing someone else who was a ballerina, it means you envy that dancer for their grace, agility, beauty and skills. You wish to improve yourself, so that you gain more confidence, and be comfortable in your skin. As you raise your self esteem, you will slowly reduce the envy for others.
If you are male, and you know how to dance ballet, then your dream of being a ballet dancer, was merely continuing a familiar theme. This dream will not hold a unique meaning for you.
If you are male, and you’re not a ballet dancer, then your dream of dancing ballet, is a hint to you, to work on your aesthetics. You have a desire to improve your grace, social skills, confidence and self esteem.