I. The Lenten fast is incumbent on all alike
On all days and seasons, indeed, dearly-beloved, some marks of the Divine goodness are set, and no part of the year is destitute of sacred mysteries, in order that, so long as proofs of our salvation meet us on all sides, we may the more eagerly accept the never-ceasing calls of God's mercy. But all that is bestowed on the restoration of human souls in the various works and gifts of grace is put before us more clearly and abundantly now, when no isolated portions of the Faith are to be celebrated, but the whole together.
For as the Easter festival approaches, the greatest and most binding of fasts is kept, and its observance is imposed on all the faithful without exception; because no one is so holy that he ought not to be holier, nor so devout that he might not be devouter. For who, that is set in the uncertainty of this life, can be found either exempt from temptation, or free from fault? Who is there who would not wish for additions to his virtue, or removal of his vice? Seeing that adversity does us harm, and prosperity spoils us, and it is equally dangerous not to have what we want at all, and to have it in the fullest measure.
There is a trap in the fullness of riches, a trap in the straits of poverty. The one lifts us up in pride, the other incites us to complaint. Health tries us, sickness tries us, so long as the one fosters carelessness and the other sadness. There is a snare in security, a snare in fear; and it matters not whether the mind which is given over to earthly thoughts, is taken up with pleasures or with cares; for it is equally unhealthy to languish under empty delights, or to labour under racking anxiety.
Source: Sermons (New Advent)