The first habit I rid myself of was never studying or doing my homework. I have replaced that habit by disciplining myself to set a specific schedule for every night. I do my homework between 8:00 and 9:00 p.m., and then from 9:00 to 9:30 p.m. I study for whatever test or quiz I might have the next day. Needless to say, my study habits and grades have improved.
The second habit I discarded was allowing myself to focus on negative thoughts. Now every time my mind turns to the negative, big or small, I have learned to think a good or positive thought instead.
The third habit I overcame was lying on a regular basis. I have learned that dishonesty will not get me very far, so I have replaced it with honesty. Telling the truth gets me farther than trying to keep up with my lies only to have to give up eventually and tell the truth when I get caught. The consequence for a mistake is always worse if I lie first.
My life has changed since I have learned that the key to conquering bad habits is to replace them with good ones.