In my sermon this past Sunday I mentioned that early Christians made the sign of the cross upon themselves as they left their homes. I mentioned this as a simple practice that helps keep us mindful of God and one that we all have time for. Making the sign of the Cross upon our bodies is a physical act that assists our prayer. It is not a replacement for prayer but is a way of assisting our whole selves to pray.
“In all our actions, when we come in or go out, when we dress, when we wash, at our meals, before resting to sleep, we make on our forehead the Sign of the Cross. These practices are not commended to us by a formal law of Scripture, but tradition teaches them, custom confirms them, and faith observes them.” (Tertullian c. 190 - c. 230)
Other physical postures we regularly use are standing, lifting our hands in worship, kneeling. At ordinations, the soon to be ordained often lay prostrate on the floor in a physical act of submission to God. People who seek a richer prayer life are usually encouraged to cultivate a place and time of regular prayer. This helps eliminate distractions. People know this intuitively. It's why most people sit in the same pew every week and why, when "our" pew is occupied the experience of worship is a little bit off. What we do with our bodies impacts our prayers. Making the sign of the Cross has a positive impact.
When we face temptation making the sign of the cross helps us focus ourselves and resist by turning back to Jesus who died for our sins. We remind ourselves of His sacrifice and the temptation diminishes in urgency. It would be nice if it went away entirely but that is a matter for many prayers.
“When tempted, always reverently seal your forehead with the Sign of the Cross. For this sign of the Passion is a symbol openly combatting the devil if you make it in faith, not in order that you may be seen by others, but consciously putting it forth like a shield.” (Hippolytus c. 170–c. 236)
There is nothing magical about making the sign of the cross. It is an act of faith not a talisman. It helps focus us. It is a physical accompaniment. Such as when people dip their finger in a Baptismal Font and make the sign of the cross. We are a people who are baptized into Jesus death and ressurection. Making the sign of the cross in this way helps us remind ourselves that we are safe so long as we remain in the waters of baptism.
But we, being little fishes, as Jesus Christ is our great fish, are born in the water, and we are safe only so long as we remain in the water. (Tertullian, Concerning Baptism c. 190 - c. 230)
No one needs to make a sign of the cross and indeed some Christians do not feel comfortable doing so. It is not part of their tradition. If its not part of yours no worries. Its utterly optional. Feel free to try it on. See if its helpful to you.
If you would like to read more about making the sign of the cross here is an interesting article on Wikipedia that goes into the differences between the Eastern and Western Church.