prove to her you will do something
prove her wrong
don't prove her right
hard as it is, take her words as lightly as you can, try not to let them bother you
she'll always love you {unless she's a sociopath, which i doubt}

Is grow up, get a job, keep a job, get your own place, pay your own bills and quit mooching off your parents to make your way.
I had a son who lived with us until he was 21, he had the Idea that saving his money was accomplished by spending other peoples money. We Finlay had to evict him to get him out where we could survive ourselves

be honest with yourself. are you lazy? do you have a history for not finishing what you've started? are you known to everyone as the proverbial slacker? if you answered yes, she might be in a panic now that your nearing adulthood. she may feel as though your not ready to be on your own. and with little evidence to the contrary, why would she?
if the answers were no...
are there things your mother felt she never accomplished in life that she wanted to? if so, she may be taking it out on you. gracefully encourage her to go after her dreams again. try something like, "so now that i'm grown up and out the house, you'll have more time on your hands to do what you want and pamper yourself."
yes or no, give your mother a big hug and lots of love (especially if the answers were yes). let her know she did the best she could to raise you, and you've grown up to be a person who goes after what they wants. tell her you plan to accomplish your goals. it will show her you've put some time and effort into considering your future options.