Firstly, I think that the distinction between "secularization" and "secularism" that Fr Cantalamessa draws at the beginning of the homily is important:
Secularization is a complex and ambivalent phenomenon. It can indicate the autonomy of earthly realities and the separation between the Kingdom of God and the kingdom of Cesar and, in this sense, not only is it not against the Gospel but finds in it one of its profound roots; however, it can also indicate a whole ensemble of attitudes contrary to religion and to faith; hence, the use of the term secularism is preferred. Secularism is to secularization what scientism is to scientific nature and rationalism to rationality.
In other words, there is a rightful autonomy of the things of the world in relation to the things of religious faith. This can be particularly recognised in the context of the project of science, where one can say that its methods and subject matter are rightly pursued in their own right and not in a subservience to a particular religion. This does not mean that science and religious belief have no relation to each other, but that there is a rightful autonomy in that relation. One could also argue that there is a similar rightful autonomy of politics from religion, though here it is perhaps more easy to recognise that this rightful autonomy does not mean that there is no relation at all. This rightful autonomy is what Fr Cantalamessa means by the term "secularization", and he distinguishes it from "secularism" which seeks to remove all presence of religious faith from the public realm.
In this sense, secularism is a synonym of temporality, of the reduction of the real only to the earthly dimension.
This then leads Fr Cantalamessa to the most striking aspect of his homily, that is, to the view that a recovery of the sense of eternal life is important for the preaching of the Gospel to others and for the living of the Christian life by those who are already believers.
In Christ, eternity entered into time, it manifested itself in the flesh; before him it is possible to make a decision for eternity. It is thus that the evangelist John speaks of eternal life: "We [...] proclaim to you the eternal life that was with the Father and was made visible to us" (1 John 1:2).This appears counter-intuitive, as we would be tempted to think that making Christian faith more "relevant to the world" would be the road of the new evangelisation. Fr Cantalamessa's development of this theme demonstrates that it is what is truly relevant to the needs of the world today.
For the believer, eternity is not, as we see, only a hope, it is also a presence. We have this experience every time that we make a real act of faith in Christ, because "you have eternal life, you who believe in the name of the Son of God" (cf. 1 John 5:13); every time we receive Communion, in which "we are given the pledge of future glory" ("futurae gloriae nobis pignus datur"); every time we hear the words of the Gospel which are "words of eternal life" (cf. John 6:68). Also, St. Thomas Aquinas says that "grace is the beginning of glory."
Fr Cantalamessa points out two implications for Christians. The passage from time to eternity involves a judgement between heaven and hell, something that he illustrates by quoting Cardinal Newman's poem "The Dream of Gerontius". And if we, today, are to direct our thoughts towards eternity it will involve us in entering in to the house of the Lord - or taking great joy in our participation in the liturgical life that takes place in our parish churches.