How do we become evil? There is no such entity to start with. Evil is the manifestation in the absence of the light.
It cannot be manipulated to do good unless the light will be allowed to enter. That is the reason that many of us becoming negative will never go to positive unless we are willing to do so. For that we need a shock to happen, an event that will reveal the light itself, like for example, Paul in the bible. Every turn may also start with a change of heart and could be little by little because of every single one of us that we consider evil has still had love in his/her heart. Even the cruelest people, dictators they have someone they loved, and they were willing to do everything for them.  Are very few that turn entirely from the light those we consider pure evil.
However, if we deny God for a long time, it will be more difficult to see the light. The cage that we create will become darker and darker, and it will stop the light to get in. All the negative energy we build, it will come to manifest in the physical plane, and that will become what we have called sin. The darker and more opaque the cage, the more afraid and evil we become. Fear is just the result of removing love of God from the picture.  We must understand that all these rich people who try to control others are the most afraid of all. That is why we see all the tools of controls, computer, and telephony system or face recognition, cameras all over the cities. Everything is built out of fear of losing control. Thinking of that, we cannot be afraid; we are only feeling sorry for our brothers who lost their ways but having the confidence that sooner or later they will awake and they will try to restore balance by opposite actions.