Holding one's tongue
"But thou, when thou prayest, enter into thy closet, and when thou hast shut thy door, pray to thy Father which is in secret; and thy Father which seeth in secret shall reward thee openly." (Matthew 6:6)
Thy Father which seeth in secret...
How loud is a silent prayer? So loud that only God (and you) can hear it. The thoughts and yearnings of our heart are meant to find no other sounding board than "Our Father which art in Heaven". There are depths to our person that no one but Him understands and sees. I find that I am filling in these heretofore uncharted spaces as I live and grow. I also realize that God was already down there waiting for me to arrive. It's like there was this doorway in the closet that led down to deeper depths than I ever knew I possessed. And now, upon returning to the surface, these territories of my person—known only to God and myself—are always there to draw upon in fellowship with Him. But only between us. No one would understand or relate to the things we share with our Father. And this is where the word "tacit" comes in. Silent agreement. It isn't that you keep these beautiful things (whatever they may be) hidden, just that you don't injure the relationship you and He share by giving out privileged information.
"Unless the Lord had been my help, my soul had almost dwelt in silence." (Psalm 94:17)
"I said, I will take heed to my ways, that I sin not with my tongue: I will keep my mouth with a bridle, while the wicked is before me." (Psalm 39:1)
The opposite of illicit, "licit" means "lawful"—allowed. After surfacing from the deep realms you experience with God, realize that, while He would have everyone in on the beauty you now know and live, not everyone is where you're at. This is very important. When Jesus is asked by the Pharisees "If Thou be the Christ, tell us plainly", to which He responds, "I told you, and ye believed not" (John 10:24-25), we see that some people can't handle the truth, literally. I find as I go about my day, the truths of God that I see and seek to live out (and in) are altogether different than the frequencies to which other people are attuned. And it's not my place to try and change them or reorient them to God's broadcast. This might sound a little odd, sure, but the point I'm seeking to express is that of keeping one's head when in and around a world that totally doesn't understand the things of God. Paul says that "the natural man (and woman) receiveth not the things of the Spirit of God: for they are foolishness unto him: neither can he know them, because they are spiritually discerned." (1 Corinthians 2:14) This is blunt. And it's best to keep one's mouth shut when, plainly, those listening have no frame of reference for what you're talking about.
"When I said, My foot slippeth; Thy mercy, O Lord, held me up." (Psalm 94:18)
Keeping one's head
"Set a watch, O Lord, before my mouth; keep the door of my lips. Incline not my heart to any evil thing. To practice wicked works with men that work iniquity: and let me not eat of their dainties." (Psalm 141:3)
It can be so easy to speak out the secrets of our hearts. God is so kind and loving and tender. He remakes us into the same. And yet we still have to keep our wits about us in a world that actively seeks to tear us down little by little. That little pilot light that was ignited upon salvation—that you and God sit around and fellowship—is constantly bombarded. From without by careless and uncaring individuals (spiritual and otherwise) and from within by a natural tendency to let slip the beauty in light of an ever-present drain (temptation) on our enthusiasm. Out of all the fronts that vie for our attention and seek to distract us from God, the one I'm most wary of is that of any other individual who would try and ferret out anything between me and God through surreptitious means. That's the killer. If God is doing big things in your life, things you don't see fully as yet (He always is.), be sure and give nothing away that belies that privileged information. It's no one's place to elicit things out of you that you wouldn't share with the devil.
"For in the time of trouble He shall hide me in His pavilion: in the secret of His tabernacle shall he hide me; He shall set me up upon a rock. And now shall mine head be lifted up above mine enemies round about me: therefore will I offer in His tabernacle sacrifices of joy; I will sing, yea, I will sing praises unto the Lord. Hear, O Lord, when I cry with my voice: have mercy also upon me, and answer me. When Thou saidst, Seek my face; my heart said unto Thee, Thy face, Lord, will I seek." (Psalm 27:5-8)
"The Lord is thy keeper: the Lord is thy shade upon thy right hand." (Psalm 121:5)