For God hath appointed to bring down every high mountain, and the everlasting rocks,
and to fill up the valleys to make them even with the ground: that Israel may walk diligently to the honour of God.
In our lives we have both excesses and deficits, which need to be rectified so that we can properly welcome Christ. We may be zealous in defending orthodoxy, but lax in self-discipline. We may spend many hours before the Tabernacle, but don't spare time to help the needy. We may extol the vitues of social justice, but neglect obedience to the Church. Excesses and deficits, Mountains and valleys, all need to be graded and smoothed to prepare the way for Christ.
This preparation is rarely comfortable, as the mountain will complain about the violence done to its heights, and the valley bewail the invasions of its spaces. Penance is not pleasant, but is necessary.
Parate viam Domini rectas facite semitas eius!