Well...remember you did something to deserve what you have. Don't complain about your punishment, do what your told, keep your grades up. Clean your room. Help out around the house. Wash cars. Sweep out the garage. These things may help you. Don't act like a martyr. Remember in the future don't do what ever it is you did again. Don't worry some day your teen years will be over and your parents won't ground you any more.
To persuade your parents to un-ground you, you will have to accept their conditions patiently. Do not argue with them and follow the ground rules effectively. If they see how obedient you are, they might lessen or even un-ground you.