A wandering mind is not necessarily a sin. It may just be a human thing, a “normal” human thing, not a “fallen” human thing. Contemplation, like all love of God, is an affair of the will first and foremost, though it can draw other faculties into it: intellect, imagination, memory, senses… As contemplation of divine things is an affair of the will, a wandering mind is really nothing much of the matter, though it would, naturally, be better not to have one.

Saint Francis de Sales puts it this way:

the will, having once tasted the divine presence, does not cease to relish the sweetness thereof, though the understanding or memory should make an escape and slip away after foreign and useless thoughts.

So not to worry. The will can be sure of what it wants, even if the rest of us is not! Just come back whenever you become conscious of your wandering mind. The mind wanders, the imagination, the senses, the intellect: sure, they all wander,

yet it is a true spiritual tranquillity, since it continues to reign in the will, which is the mistress of the other faculties.

And therein lies the specificity of Christian contemplation. It’s not an intellectual affair. It requires no lengthy psychological adjustments and preparations. It’s suitable for all: adults, children, cloistered, non-cloistered, busy or not. Christian contemplation is just divine love, thrown into our soul in inflame it and set the whole world alight. And the justified will, rightly and truly mistress of the other faculties, is never their victim so much as they are hers.