Contextually, this is when David is saying Solomon, of his many sons, will be the one to follow him as king. Interestingly enough, it is a charge to build God's temple. God has told David that he is not to build the temple because he has shed blood, but that his plans should be given to Solomon to complete. Fascinating. Is this a sort of shift, I wonder... I have not read closely (yet) the stories surrounding this to see if this is some sort of change that indicates the spilling of blood is not favorable to God. I'll have to see if this theory is substantiated at all...
In itself, I like the quote's emphasis of strength, courage, and action. It seems fitting as the next step to conquering fear... Let's say this is working on me, that I am less afraid. Great! Right? But then what? Do I use that for self-serving purposes? It is not enough just to sit at home unafraid, I need to (we need to) take that unafraidness, that calm, out into the world to alleviate fear in others.
For an explanation of this Fear Not series, read my first post on the nature of fear.