This world was good when it was created, but since sin entered it, it became subject to darkness. The first humans according to the Bible were Adam and Eve. They were created by God in holiness and perfection. They were created in the image of God. Death had no authority over them. Thus, they were eternal beings, until they sinned. Since that time Adam and Eve got to know good, but also evil and humanity went under the domain of death. Jesus Christ came to save us, and "for whoever believed in him, he gave them the right to become children of God" (John1:12) Thus, even though we might be good, and even if we are saved, the darkness in this world is always going to hurt us. God might let these things happen for many reasons. The first reason is that He might be letting us go through tests, the second reason is that it might be a consequence of our wrongdoings, and the third reason is that He might be trying to bless us. God's blessings are not always preceded by good things, they might come after tribulations and difficult times. Other reasons that God might have to let difficult things come over us are: to make us wise, to make us stronger, to teach us a life lesson, or to make us humble.