How is Gene going to approach life now?

This depends on what point in the story you are referring to.

at the end of chapter 5

Gene visits Finny at his home in Boston. Gene blurts out that he caused Finny's accident. Finny lashes out at Gene saying he does not believe it and to get out. I'm not sure that Gene really knows what to do at this point. He is glad he told the truth but is confused with Finny's reaction.