In the Catechism, para # 1303 includes the following quote from St. Ambrose----
Recall then that you have received the spiritual seal, the spirit of wisdom and understanding, the spirit of right judgment and courage, the spirit of knowledge and reverence, the spirit of holy fear in God’s presence. Guard what you have received. God the Father has marked you with his sign; Christ the Lord has confirmed you and has placed his pledge, the Spirit, in your hearts.
What does “Guard what you have received” mean? Guard the gifts of the spirit for you can lose them?