Here is an opening litany and prayer for a Blue Christmas or Longest Night service during Advent. It comes from a longer Blue Christmas liturgy (When Christmas Hurts). See below for link.
Opening Responses for a Blue Christmas service
The Grace of our Lord Jesus Christ,
the love of God,
and the fellowship of the Holy Spirit
be with you all.
And also with you.
The people who walked in darkness have seen a great light;
on those who live in a land of deep shadow, a light has shone.
For the yoke that was weighing upon them,
and the burden upon their shoulders,
you have broken in pieces,
0 God, our Redeemer. (Isaiah 9:1-4)
Let us pray:
God of mercy,
hear our prayer in this Advent season
for ourselves and for our families
who live with painful thoughts and memories.
We ask for strength for today,
courage for tomorrow
and peace for the past.
We ask these things in the name of your Christ,
who shares our life in joy and sorrow,
death and new birth,
despair and promise. Amen.
~ from a complete Blue Christmas liturgy (“When Christmas Hurts”) posted on The Young Clergywoman Project blog. http://youngclergywomen.org/blue-christmas-service-when-christmas-hurts/