You said it yourself, it requires training to control the dark side. Not use it chaotically. Like Rey did. Like Savage did. They didn't just get angry, they let anger to control them, dominate. That's the way to the dark side. But Rey unlike Savage, didn't want to succumb to the dark side. Hence she took Kylo's fighter, flew it to the island planet and burned it - essentially stranding herself there.
So you are contradicting yourself.