Spiritually speaking, we've all experienced what it means to walk in darkness. At the time, however, we probably didn't realize we were walking in it. Darkness was what we were accustomed to. Darkness was what we knew best. And since most of the people in our lives were also walking in darkness, it really didn't seem out of place to us.
But God did not design us to walk in darkness. It isn't His desire that we do so. As Jesus was revealing His divine nature to groups of Jewish religious leaders, He explained that He is the light of the world. Those who follow Him will not walk in darkness any longer, but will experience the light of true spiritual life.