Hello Doctor, I Have Consume A Chewing Tobacco But Now

Hello doctor, I have consume a chewing tobacco but now I started to stop using this because I think it has effect on our health mainly on memory which retarded so I want to give up, I want to improve my memory because I want to crack a competitive exam and wanna memoru strong so here I want to know is that how can chewing tobacco pan effect memory and improve from this csuses.