There is no need to be afraid, in five more days Our Lord will come to us. (Benedictus Antiphon for December 21)
And here is the reason why the Mass was traditionally said facing east, ad orientem. (The reason for facing east is not "because that's where Rome is" as a local woman very authoritatively informed a friend of mine.)
From the earliest times, Christians at prayer have turned towards the East. Christ is the Dayspring, the rising sun who dawns upon us from high “to give light to those in darkness and in the shadow of death” (Luke 1:9). The eastward orientation of churches and altars is a way of expressing the great cry of every Eucharist: “Let our hearts be lifted high. We hold them towards the Lord.” When, in the celebration of the liturgy, the priest faces east, he is “guiding the people in pilgrimage towards the Kingdom” and with them, keeping watch for the return of the Lord. “This Jesus, who was taken up from you into heaven, will come in the same way as you saw him go into heaven” (Acts 1:11).Share
The Eastern Churches follow to this day (and the Western Church is in the process of recovering) the apostolic tradition of celebrating the Eucharist towards the East in anticipation of the return of the Lord in glory. A powerful witness is given in the prayer of a priest and people who stand together facing eastward and giving voice to the same hope. “The Spirit and the Bride say, ‘Come.’ And let him who hears say, ‘Come’” (Ap 22:17).