“In him was life; and the life was the light of men.”  
John 1:4

There is a light ‘for’ men; that when they receive, they would never walk in darkness, that light isn’t a physical lamp that can be stolen, but a life to be received.
Anyone who has received that life has no reason to walk in darkness.
Jesus said:
“Then spake Jesus again unto them, saying, I am the light of the world: he that followeth me shall not walk in darkness, but shall have the light of life.”  John 8:12
He also said:
“For as the Father hath life in himself; so hath he given to the Son to have life in himself;”  John 5:26
The life in him, is the life in the father, the life of the father is the life he brought for us; that when we receive, we would never walk in darkness.
Step one to following him is receiving his life, no one can follow him without living the life he lives. It will take some effort for a cat to follow a dog or a grasshopper to follow a bird, they are different species. A human can try to follow Jesus but will never do it well enough until he becomes just like Jesus- a new creation with the life of the father.
It is awesome to know that because of the life you have received, you can be all that Jesus is and on the earth, insight and understanding would always be available to you, because through the word of God, you would always know the right way to think, talk and act in that seeming ‘darkness’.