This song is basically about that time in your life when you realize that the people around are not beneficial to you. People who aren't striving towards the same goal as you and who are bringing you down. They say "If you can't change the people around you, Change the people around". There are certain people you have to cut off.
I recently found out about Kendrick Lamar through a friend and he's pretty dope. If you like Hip-hop I suggest you listen to him(ya know, if you don't already).