Building walls

Asa, King of Judah, destroyed idols and encouraged the people to follow after Jehovah. The Bible then states that the LORD gave them peace. While they were at peace Asa fortified the cities (he built walls with towers and gates). I believe that there is the principle here of that when we are at peace (not battling) the enemy we should strive to fortify ourselves. The principle is easily understood, but how is applied to our day? I think one of the guiding principles to all biblical application is to understand that the Kingdom of God is within. It deals with the spirit of a man. Of course what is changed in the spirit will have an outer flow into the rest of the one's being, but the principle focus should rest on the change of the spirit. If we take that into consideration, I think the practical application of Asa's example is fortification of the spirit. How is the spirit fortified? I do not limit it to these two things but what comes to mind now are: meditating of God's word and praying in the spirit. Throughout the word of God meditation upon His word is related as a pivotal way of having it become a part of one's spirit (as one thinks in his heart so is he). Praying in the spirit is defined as building upon one's faith. Thus, we should pray that the LORD would help us to fortify ourselves when we are at peace.