"...the faith and love that are in Christ Jesus" (1 Tim. 1:14 and 2 Tim. 1:13).
Think again about the cross. Think specifically about its shape. It moves in two directions: up and down, and side to side. Vertical and Horizontal. One without the other is not the cross.
What does it mean? Our Lord could have died in other ways. He chose crucifixion. Could it be that He chose it in order to make a lasting picture of His entire teaching? For He taught us to love and trust in God (vertical) and to love and serve our neighbor (horizontal).
But it is not only the wood of the cross that moves in two directions. It is, really, Christ Himself. He is our peace with God (vertical) and with each other (horizontal).
Next time you hear the words of the Post-Communion Collect ("in faith toward You and in fervent love toward one another"), think of the cross - the cross of Christ.