Why do we cross ourselves?

Please tell me, Maggie, other than it being a holdover from our days of Catholic faith, why do we cross ourselves and when is it appropriate?
Wondering in West Little Rock
Dear Wondering in West Little Rock,
Ah!  The sign o’ the cross is one of my favorite gestures.  It’s a way ta pray with my body, reminding meself that I’m blessed.  People have been makin the sign of cross on themselves for a long time now in different ways.  Early on it was just a tracing of the cross on yer forehead with yer thumb.  The 3rd century theologian Tertullian said, "We Christians wear out our foreheads with the sign of the cross.”  By the 4th century people had started crossing their whole bodies and made up about as many interpretations of the meaning as there’s stones out on the heath.  The thing to remember is that the sign of the cross is a kind of body prayer to help ya move yer whole self toward God.  Use it when it is helpful to yer worship, don’t when it isn’t.
When we worship together we’re all there to play a role in the big prayer to God we call the Eucharist. Here are some times in the service ye might wanna cross yerself:
+ When the celebrant announces the Holy Gospel (here we cross our forehead, lips, and chest as a sign that we profess the truth of the gospel with our mind, lips and heart).
+ The Nicene Creed: “And the life of the World to come.”
+ Prayers of the People: When we pray for those who have died.
+The Absolution: At the words, “Have mercy upon you; pardon and deliver you”
+The Words of Institution: When the celebrant elevates the Host and then the Chalice.
+ Epiclesis over the people: This is when we call on the Holy Spirit to bless us, usually after we’ve asked the spirit to descend and bless the bread and wine.
+ At the altar rail, either before or after receiving Holy Communion.
+The Benediction: “The Blessing of God Almighty, the father, the Son and the Holy Ghost”
I hope that helps ya, Wondering!  I’m always ready to answer any more of yer questions.
God’s peace be with ya!
St. Maggie