It is appropriate to do so, actually, because those living behind a grille look into the same foyer (or "reception room") day after day. And in the analogy of the cloistered heart, so do I. I think of the "foyer"as my mind, the place where thoughts wander in and out.
I do not have total control over what thoughts gain access to the parlor. Even to walk through a mall or glance at a newspaper is to open the doorways of my senses to a multitude of ideas. However, I do have some influence over what thoughts enter in the first place. If I go to a movie in which I know there are fear-inducing or lustful scenes, I am giving disturbing thoughts free access to the foyer. If I listen to gossip, I'm opening my mind to uncharitable judgements. If I dwell at length on how I have been "wronged," or on how bad I feel today, I am setting myself up for self-pity My intention may not be to have negative, unloving, self-focused thoughts lingering around - but once these have been admitted, they often set up camp and yammer at me through the grille for days and weeks to come. These can do much to distract me from God and His will for me. They can cause my mind to wander into areas where I do not want it to go. They can, if I don't boot them out, lead me into sin.
Over the years, I've collected a few choice "pieces of grillwork" that help me gain some perspective....
"Our thoughts should be wholly directed to all that is true, all that deserves respect, all that is honest, pure, admirable, decent, virtuous, or worthy of praise." (Philippians 4:8)
"We.. bring every thought into captivity to make it obedient to Christ." (2 Corinthians 10:4-5)
"Certain attitudes deriving from the mentality of 'this present world' can penetrate our lives if we are not vigilant." (Catechism of the Catholic Church # 2727)
"Close your ears to the whisperings of hell and bravely oppose its onslaughts." (St. Clare)
"Do not conform yourselves to this age but be transformed by the renewal of your mind, so that you may judge what is God's will, His good, pleasing and perfect will." (Romans 12:2)
"Disown by a brief and simple act every kind of thought that is contrary to divine love, saying: 'I renounce all thoughts that are not for You, O my God; I disown them and cast them off forever.' And then when they attack you, you do not have to do anything except to say from time to time: 'O God I have rejected this, You know I have.'" (St. Francis de Sales)
"Temptation gives you a chance to show Me your fidelity." (Jesus to St. Faustina)