Not really, if you funder mentally are a liar/cheat/angry. In the short term you can pretend to not be that person.
I think people who have 'changed' were whoever they were through circumstances not as a natural character.
Look it like mental health. Some people are not wired right, for example murderers. Some murderers show psychotic symptoms their whole life and go on to plan and carry out horrific acts. Some people kill other in the heat of the moment or even by accident. I believe the later people can be reformed the first not.
Do you see what I mean?