It's really in your flesh and blood, you can't change until you decompose. there are practices that includes mass level of body recycling while alive, or burning your entire karma( just a term) , until you basically don't remember much of your past. Doing so can be dangerous aswel cz you gonna lose your centre motivation, and unless you can build something new you'll go mad, I don't know how much time it takes to build it, could be 7 years or more ( source inner alchemy).