This simple explication of what is summed up in the ancient phrase lex orandi, lex credendi - rule of prayer, rule of faith. If we accept what he says, it tells us the when the faith is waning, we must look at liturgical practice for the antidote. It's not the only reason that it might be happening, but its the first place we should look, I suggest. Furthermore, given that the contemporary culture is an incarnation of the core priorities and beliefs of society, the greatest weapon we have for the evangelization of the culture is the liturgy. This is how we create a culture of life, which is what the Cardinal is addressing in his response.
You can read the full interview here.
As an aside, this is precisely the principle that Leila Lawler and I had in mind when we wrote our book, The Little Oratory - A Beginners Guide to Prayer in the Home. This is promoting the idea of liturgical piety in the home that is derived from and points to the Mass. The Liturgy of the Hours is an overflowing of the Mass into the day and into our daily lives and the praying of the Liturgy of the Hours, therefore, is a supernatural key to the ordering of every aspect of our lives in accordance with a liturgical piety. So as well as focussing on the most important matter of the Mass, we should consider also the Liturgy of the Hours. Accordingly all Catholic devotions which are an essential aspect of Catholic culture too, for example the Sacred Heart, should support rather than distract from our liturgical practice. When all of this is harmonised the life of prayer is one that makes ordinary living easier and not (as one might believe sometimes) a burden - an ever increasing list of things that I feel I ought to be doing, accompanied by and ever increasing sense of guilt when I fail to do them all.
