"Let me assure you that this was not an easy or hasty decision. As I stated, I, along with those closest to me, have put a lot of time, deliberation and prayer into this decision and I truly am at peace with it," Johnson wrote. "I also want you to know that I have the utmost respect and admiration for the game of football. It has provided so much for me and my family and I will be forever grateful to the game."