Evagrius. "On thoughts".
26. How to Acquire the Knowledge of Discernment.
If any of the hermits wishes to receive from the Lord the knowledge of discernment (diakrisis), he should first work eagerly at the commandments that are at hand [in his power], not omitting anything. And so at the time of prayer he should request knowledge from God, who gives generously to all without reproaching; but let him ask without doubting (Jas 1:5), not thrown about by waves of doubt (cf. Mt. 8:24) , and it will be given him (Jas 1:5).
For it is not possible to receive knowledge of even more matters if one has been neglectful of those matters already known otherwise, having transgressed greatly one would be answerable for even more sins.
And it is a blessed thing to serve the knowledge of God, for it is truly dangerous not to do what [such knowledge] advises, and it is blessed to do all that it teaches.
The nous [wanders in] circles when it is impassioned (empathēs) and becomes difficult to restrain when it reflects [within itself] on matters that produce pleasures.
But it ceases to wander when, having attained apatheia, it meets the incorporeal [beings], who fulfill its spiritual desires (epithumias).
HOWEVER, it is impossible to receive knowledge without having made the first, second, and third renunciation[s].
The first renunciation is to voluntarily leave all worldly things for the knowledge of God; the second is the casting aside of evil which occurs through the grace of Christ our Savior and the zeal of the human person; the third renunciation is separation from ignorance concerning those things that are naturally manifested to people in accordance with their state.