We have a moral duty to support, maintain and protect a constant and unfaltering connection with our "personal" Mythos.
As regards what Gide says above, I refer to this indelibly unique part of ourselves as our “MYTHOS.” It is something that is with us from birth, and it remains with us throughout our life.
From the very first , it accompanies us and helps to guide our thoughts and our actions. It is wise in ways that we cannot yet know, and it helps us to properly learn and to grow.
Its presence and vitality are what we are protecting when we protect children from negative or damaging external influences. To the best of our ability, we must vigilantly defend their innocent spirits from traumatic limiting effects, until they are ready enough to defend themselves.
At a certain point, as children, we become aware of this connection to our Mythos … aware of the existence of that “mystery” within us which guides us, which supports us, and which offers us access to a world of limitless possibilities … limitless so long as we support it, respect it and continually make ourselves open and available to its guidance and influence. Ideally, it should be strong and as easy to experience as a brilliant birdsong.
It is all too easy to lose the connection to this source of inspiration as we grow older, and so let ourselves start to feel that we are not gifted in any special way … but that we do what we do and if we do it passably well, sometimes we will surprise ourselves, once those heavenly gifts of the Mythos are replaced by the worldly rewards of “trying” … which informs us that we should live our life as it is defined for us by the generally accepted “habits” and patterns of the everyday world.
That is not what Gide is saying here. He is saying we have a moral duty to support, maintain and protect a constant and unfaltering connection with our "personal" Mythos.
In that sense, art is never something you do, it is rather always something you are. It is a process; it is a verb that unites you the subject to the object of your imaginings.