These are my reasons and they should be your reasons as well. They are:
1) It reminds me of the priceless gift the Son of God gave to us all.
“And as Moses lifted up the serpent in the wilderness, so must the Son of man be lifted up, that whoever believes in him may have eternal life. For God so loved the world that he gave his only begotten Son, that whoever believes in him should not perish but have eternal life. (John 3:14-16)”
2) There is power in the Cross.
“For Jews demand signs and Greeks seek wisdom, but we preach Christ crucified, a stumbling block to Jews and folly to Gentiles, but to those who are called, both Jews and Greeks, Christ the power of God and the wisdom of God. (1 Corinthians 1:22-24)”
3) The Church recommends it.
“The sign of the cross, on the threshold of the celebration, marks with the imprint of Christ the one who is going to belong to him and signifies the grace of the redemption Christ won for us by his cross. CATECHISM OF THE CATHOLIC CHURCH paragraph 1235”
4) I am not ashamed of Christ who died on the Cross for me.
“For the word of the cross is folly to those who are perishing, but to us who are being saved it is the power of God. (1 Corinthians 1:18)”
5) I am not ashamed of the Gospel in which the Cross was an essential part.
“For I am not ashamed of the gospel: it is the power of God for salvation to every one who has faith, to the Jew first and also to the Greek. (Romans 1:16)”
6) I love the Blessed Trinity a lot.
I am the child of God the Father via adoption. I am a member of the Body of Christ. I am a temple of the Holy Spirit. “Go therefore and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, teaching them to observe all that I have commanded you; and lo, I am with you always, to the close of the age. (Matthew 28:19-20)”
7) The early Christians were fond of making the sign of the Cross.
“In all our travels, in our coming in and going out, in putting on our clothes and our shoes, at table, in going to rest, whatever employment occupies us, we mark our forehead with the sign of the cross. ~ Tertullian of Carthage, 3rd century Christian, Father of the Church and renowned Apologist”
8) It’s Christian.
It’s cool to be Catholic!
9) It’s a devil repellent.
The devil and all the forces of evil get pissed off!
10) Saint Paul of Tarsus knows what’s in the Cross for Christians.
“For I decided to know nothing among you except Jesus Christ and him crucified. (1 Corinthians 2:2)”