From the same:
- The Eastern heritage is more than just liturgy
Certainly, the tendency to reduce the specific heritage of the Eastern Churches to just its liturgical dimension should not be encouraged. The attraction exerted by the sacredness of the rites, the intense emotion arising from the poetic dimension of the texts, has possibly led to an excessive emphasis of the exterior or emotional aspect, an easy place of refuge for those who deny the liturgy its necessary link with life. This is what has sometimes led the same Eastern Catholics to perceive only the liturgical patrimony as being specifically their own, conforming themselves instead, for the other aspects of spirituality, to the Western sensibility considered as common to the Universal Church. Rather, the value of Eastern theologies and spiritualities, understood as part of the undivided heritage of the Universal Church, is a fairly recent discovery, as is the emergence of the importance of particular disciplines.
The practice of the Eastern liturgy without its entire heritage flowing into it, as into its highest expression, would risk reducing it to pure superficiality.
From UNITATIS REDINTEGRATIO from Vatican II: