Even if the Christian God exists, how can you be sure he wants what's best for you as an individual?

Think about it. I'll even grant you that he's not the sadistic Calvinist God. He wants everybody to be saved. But not everybody can or will be saved. He wants person A to be saved, but for some reason it's more important for person B to be saved. In order for person B to be saved, Person A must suffer indescribable suffering in earthly life, ending in his cursing God and going to hell. It's all for the greater good, but not for person A's good. So Person A dies homeless, jobless, legless, armless, and horribly scarred. As a result he loses his faith and goes to hell. But it's all God's will! What do you think of that?