Psalm 15:5b - "He who does these things will never be shaken."
I don't want to be shaken - do you? Most of us want to be on firm ground, standing tall. What does a person have to do to avoid being shaken? The psalmist asked a question about who can dwell with God in Psalm 15:1 and proceeded to describe the kind of person who can. He, whose walk is blameless, is righteous, speaks truth from the heart, no slander is on his tongue, does his neighbor no wrong, casts no slur on his fellowman, and on and on. The person who does these things will dwell with the LORD and he "will never be shaken."
Dwelling with the LORD for a Christian, means spending time with Him in prayer and in His Word. The person who spends quality time with God is the person who will be blameless (without willful sin), righteous, honest, etc., and the one who "will never be shaken."
Everyone is a little shaken at times, but the one who dwells in God's presence on a continuous basis, will not be shaken permanently. God brings us back to a firm foundation and we will be strong in Him.