At the heart of catechesis: Christ
Whoever is called "to teach Christ" must first seek "the surpassing worth of knowing Christ Jesus"; he must suffer "the loss of all things. . ." in order to "gain Christ and be found in him", and "to know him and the power of his resurrection, and (to) share his sufferings, becoming like him in his death, that if possible (he) may attain the resurrection from the dead".
Source: Catechism of the Catholic Church (Vatican.va)