"Practicing the Invisible", at first might bring to mind an image of someone carefully practising that great new dance sweeping the nation, "The Invisible". Imagine the Prima Ballerina at center stage, executing the most amazing Pirouettes and Arabesques, only to be completely ignored by the other dancers, who do routines of their own, as if she were not there. They avoid making contact with her seemingly by pure coincidence.

Then again, "Practicing the Invisible," may refer hiding in plain sight, like a ninja warrior dressed as a lowly beggar. Maybe it means to be invisible to one's enemies, like a member of the Witness Protection program. I prefer to break the title down into two parts: "Practicing" and "The Invisible." I think of Practicing as in "going into practice" such an attorney who joins the bar and opens his own law practice. As for "the Invisble", I can't help but recall the phrase from -Antoine de Saint -Exupery, author of "The Little Prince": Voici mon secret. Il est très simple: on ne voit bien qu'avec le cœur. L'essentiel est invisible pour les yeux.
Here is my secret. It is very simple. It is only with the heart that one can see rightly; What is essential is invisible to the eye.
 Here, we have finally touched upon what I think you mean when you say that your memoirs should be titled "Practicing the Invisible": it is that you have learned, you have studied long, and passed the bar exam, and opened your own professional practice. It is a practice that uses drawings, paintings, photographs, and especially word pictures to convey the essence of what cannot be seen by the eye: the beauty and ecstasy of communing with Him to accomplish His great plan. To practice the invisible is to study, meditate, learn, and grow in the common-sense wisdom found in the Beatitudes and throughout His scriptures. It is practicing these essential things that can not be directly seen by the human eye, to the point that you can "go into your own practice" like a professional doctor or lawyer.