Our aim is to know God in a direct way, not intellectually or through reason. This is often referred to as receiving the light of Christ. When we receive this light we experience a sense of joy. When it is a light sent by the devil we feel a bit of agitation or obscureness.
Saint Seraphim says,
The Christian heart, when it has received something divine, does not demand anything else in order to convince it that this is precisely from the Lord...
Saint Seraphim also gives many pointers about how to prepare to receive this gift of light.
To receive and behold in the heart the light of Christ, one must, as far as possible, divert one's attention away from the visible objects. Having purified the soul beforehand by repentance and good deeds, and with faith in the Crucified, having closed the bodily eyes, immerse the mind within the heart, in which place cry out with the invocation of the name of our Lord Jesus Christ; and then, to the measure of one's zeal and warmth of spirit toward the Beloved, a man finds in the invoked name a delight which awakens the desire to seek higher illumination.
What is important to remember that this gift comes after we have purified our heart and soul of its attachment to the passions of the body and one is committed to a life of ongoing repentance and good deeds, including participation in the sacraments of the Church.
Saint Seraphim goes on to describe this gift.
When a man beholds the eternal light interiorly, his mind is pure and has no sensory representations, but, being totally immersed in contemplation of uncreated goodness, he forgets everything sensory and wishes not even to see himself; he desires rather to hide himself in the heart of the earth if only he not be deprived of this true good--God.This is the gift that is available to all who are willing to cooperate with God and undertake the necessary preparation.
Reference: Little Russian Philokalia, Vol 1, pp 46-47