Psalm 21:7 For the king trusts in the LORD, And through the lovingkindness of the Most High he will not be shaken.
David, the king, says that he trusts in God and because of that he will not be shaken. In some of the previous chapters, David has called God his rock. When our foundation is our trust in God, we will not easily be shaken. Storms will come, the winds will blow, water will splash and yet you will stand strong.
Jesus told a parable about this in Matthew 7. He talked about the foolish man building his house on the sand. When the rains came, the house fell down. But the wise man built his house on the rock. When the rains came the house stood firm. The wise man builds the foundation of his life on Jesus. He is able to stand firm in the tough times. The foolish man falls apart when the storms come.
Trust in God and build your foundation on Him. He is our rock!