“My truck won't start, wife ran off with my best buddy, my dog don't love me no more and on top of all that, we just had a nasty church-split. God has me going through a real dark night of the soul!”
Dark night of the soul.
If you've been around the church for any time, you've probably heard people use this phrase to describe substantive black and difficult periods in their lives, typically a bit more trying than the hitches our good ol' boy here is experiencing.
These are times when God seems so far away if not altogether absent and trials of spiritual drought and life problems are one's constant companion. This dark night tests and torments the depths of our soul. You know it when you're in it.
The phrase comes from John of the Cross, a sixteenth-century Spanish priest who came to work with Teresa of Avila in her effort to reform the Carmelite Order. He was one of Spain's greatest poets. He addresses this dark night in two major writings, The Ascent of Mount Carmel and The Dark Night. Both of these books make up two different commentaries on one of his many poems. This piece starts:
One dark night,
fired with love's urgent longings
– ah, the sheer grace! –
I went out unseen, My house being now all stilled
But John of the Cross' “dark night” is not what most think it is or how they use it. While it is indeed an experience one goes through, it is not something that happens to us, nor does it refer to the circumstances of life that affect our souls. The “dark night” John is referring to is something a disciple of Christ intentionally enters into, a particular mindful practice of a spiritual discipline.
How does the poet himself describe it? Right out of the gate, in his commentary on the poem, he explains to us:
In this first stanza, the soul speaks of the way it followed in its departure from love of both self and all things. Through a method of true mortification, it died to all things and to itself. It did this so as to reach the sweet and delightful life of love with God. And it declares that this departure was a dark night. As we will explain later, this dark night signifies here purgative contemplation, which passively causes in the soul this negation of self and of all things.
The soul states that it was able to make this escape because of the strength and warmth gained from loving its Bridegroom in the obscuring contemplation. 
“Purgative” is a word he uses often through this work, for it speaks of that which is sought and experienced by the disciple who enters this spiritual process. In his usages, the term refers to an emptying. In The Ascent of Mount Carmel, John explains that this process gets its name because, “in . . . them the soul journeys in darkness as though by night.”
This process or exercise is largely about what Augustine referred to in his book City of God as ordo amoris: the proper ordering of the loves. To be virtuous, the Christian should make sure that each love in one's soul receives the degree of attention appropriate to it, not more, not less. John explains,
When the soul reaches the dark night, all these loves are placed in reasonable order. This night strengthens and purifies the love that is of God, and takes away and destroys the other. But in the beginning [due to its soul-testing rigor] it causes the soul to lose sight of both of them.
As serious Christians, we should honor our spiritual forefathers on whose shoulders we stand by speaking correctly and truly of important facets of the various disciplines and spiritualties that many in Christ's Body practice and have practiced for hundreds of years. If we choose to use such terms, let us go to the original source to learn their meaning, rather than from the last person we heard use it. Referencing gems from the wealth of our faith requires more than playing the telephone game. But too often that is precisely what we do.
The sacred history of Christian practice is worth exploring, knowing about, and referencing accurately. But we can and should be more diligent about how we use spiritual and theological language.