“Do good in Thy good pleasure unto Zion: build Thou the walls of Jerusalem.” (Psalm 51:18, emphasis mine)
It takes time to build walls. One stone upon another all the way down the line. David prays to God to do this thing. It’s something (the building of walls) that must be done by Him alone in order to prevent any unwanted influence from coming in and taking over. When the enemy looks to besiege your heart, you want to rest assured, knowing that God has put up the barriers that will keep him out.
“He (and she) that hath no rule over his own spirit is like a city that is broken down, and without walls.” (Proverbs 25:28)
Walls aren’t all bad. If we have grown out of childhood but don’t understand at our core that this world will do its level best to snuff out the light of God, we need to repeat a grade or two. Jesus says that “it is your Father’s good pleasure to give you the Kingdom.” (Luke 12:32) This means, among other things, that God wants to fill you with the good things of Heaven. He wants to see Heaven blossom and take shape in your life and then branch out. But unless those ramparts are there, staving off the inevitable attacks of the devil, God’s holiness cannot keep the gifts for/in our lives operable. For instance, say you have the gift of joy. Now, “joy” is one of the fruits of God’s Spirit (see Galatians 5:22-23). And we all know that “the joy of the Lord is your strength.” (Nehemiah 8:10) But if you don’t understand that “in [God’s] presence is fulness of joy” (Psalm 16:11), and that by worshiping and praising Him, His presence is ensured (He “inhabitest the praises of [His people]” Psalm 22:3), the joy will sluice and drain out of your life, leaving you powerless and at the mercy of the enemy. Just joking, the enemy has no mercy. Mercy comes from God alone (see Psalm 130:3). God’s joy is ours for the asking, and the way to appropriate it after asking and then receiving it by faith is to worship and praise Him. But again, the walls. There are people and influences and atmospheres all around us that we must keep out, however politely. Because God’s joy is like an heirloom seed. It is given and it’s meant to produce fruit in your life. Ask Him to build the necessary walls in your life so that He can give you more than what you had before.
“And I arose in the night, I and some few men with me; neither told I any man what my God had put in my heart to do at Jerusalem: neither was there any beast with me, save the beast that I rode upon. And I went out by night by the gate of the valley, even before the dragon well and to the dung port, and viewed the walls of Jerusalem, which were broken down, and the gates thereof were consumed with fire.” (Nehemiah 2:12-13)
If, for whatever reason, you have walls that are destroyed and that you can’t seem to rebuild to save your life, pray. Ask God to reveal whatever it is keeping them unbuilt and for Him to begin building them one brick at a time. While this may be the 21st century and the idea of self-contained cities unconnected by thoroughfares or shared counties is certainly anachronistic, the heart-interior of individuals is different. We need these partitions that would screen our influences and ensure God can get done in our life (and in this world) what He wants. Of course, we can help Him along:
“Keep thy heart with all diligence; for out of it are the issues of life.” (Proverbs 4:23)