+ JMJ +
2) Like Mother Teresa, I go to look at God and give Him time to look at me.
1) To adore God.
2) To thank God.
3) To obtain grace.
4) To offer a Reparation to God for our sins and the sins of the whole world.
(Suggestion for kids: Perhaps you can offer up the times when you find yourself bored at Mass. Let's offer up that "suffering" for souls.)
The Catholic Mass by Fyodor Bronnikov (Source)
To receive the Body, Blood, Soul, and Divinity of our Blessed Lord in the Holy Eucharist.
To personally stand at Calvary and witness the sacrifice of the Living God. (I imagine this with my mind's eye when I look at the altar during Consecration.)
To offer my life (prayers, works, joys and sufferings, my whole being) to God, in union with the Sacrifice of the Lamb of God.
Being at Mass is our way to Him and His Way to us through His Priests.
Because missing Mass -- without appropriate reason or unforeseen circumstances that prevent one from going -- places the person in a state of mortal sin.