I know everyone who watched the season premiere last week and heard these lines thought to themselves, "Holy crap, the chief is talking to me." And then proceeded to bawl and shove cookies in your mouth because that episode was so stressful.
These lines really apply to letting go of things, be it a memory from your past or doubts about your future. Deciding is a huge part of letting go. You have to choose what life you want to live. Do you want to let this thing hold you back or do you want to move on and kick ass at life? The choice is simple. It's the decision that's hard.