Catholic tradition says that there are four comings of Christ. All of them are mentioned in the Advent Liturgy. The first is His coming in the flesh. The last is when He comes again in glory. But between them are two more: Christ comes into our hearts, and Christ comes for us at our death. The purpose of this season is to prepare us for all of these "advents".
In hora mortis meae voca me.
Et iube me venire ad te,
Ut cum Sanctis tuis laudem te
in saecula saeculorum.