Appropriately, these final exhortations concern all aspects of life, the internal and the external, what we think and what we do. The mind is never idle. It is always occupied with something. Given this, it requires effort to constantly feed the mind with wholesome food. And though the amount of unwholesome food for the mind is rife, there is much wholesome food for thought to chew on as well.
Truth is so important.
There is so much that is false in the world. May God be praised that we know and understand the truth of the gospel. May He be praised that we can seek truth and find it in the gospel. All that is in the Bible is worthy of meditation. It is the truth of God.