carelessness is like a disease you can catch. and will bother you all the time. You can be super smart like me. But you can still be careless. you can play sport. and be the best. but you can still be careless. to fix carelessness you can. You can overcome the carelessness by meditation for at least twice a day for 15 Min's.
And learn yoga which will give concentration power, good memory and it will remove your carelessness and build a willpower in your mind.
Try you will sure get sucess in your life. Also read the bible and try to follow the way of god.