the bad effects of love

As for ~love~, there are blemishes also. Among these is the fact that the lover, as a result of his preoccupation with the goodness of his beloved, is heedless of the beloved's defects:

"Love of anything brings a blindness and a deafness".

"Anyone who loves something, his sight becomes defective and his heart sick" -Nahju 'l-balaghah-.

The relation between headlessness and love
~Sa'di~ wrote in his ~Rose Garden~ (Gulistan): For everyone it is the same, one's own mind seems perfect and one's own child beautiful. This bad effect of love is not inconsistent with sensitization of the intelligence and perception that are another effects of love. Sensitization of the intelligence means that it brings man out of slow-wittedness, and actualises his potential. However, the bad effect of love is not that it dulls man's wits but that it makes man heedless, and the question of intelligence is different from that of heedlessness. Very often, as a result of the preservation of a balance in sensibilities, dim-witted persons are less prone to heedlessness.

Love makes the understanding more keen, but the attention one-sided and one-tracked. Thus, we said before that the property of love was singleness, and it is as a result of this singleness and focality that the defect arises, and attention to other things diminishes.

The relation between connivance and love
What is more, not only does love cause defectiveness, but it shows the defects as something good; for one of love's effects is that wherever it shines its light, it makes that place seem beautiful, it turns one speck of goodness into the sun. It even makes black seem white and darkness light. As ~Vahshi~said:

"If you sat in the ball of my eye, Naught would you see but the goodness of Layla"

And it is perhaps for this reason that love is unlike knowledge, which is completely a function of what is known. Love's inward and psychic aspect is greater than its outward and real aspect; that is to say, the equilibrium of love is not a function of the scales of goodness, but more a function of the scales of the potentiality and essence of the lover. In fact, the lover has an essence, a matter, a latent fire which is seeking an excuse, an object. Whenever it happens to encounter an object and finds compatibility - the secret of this compatibility is still unknown, and that is why it is said that love is unreasonable - this inner potentiality manifests itself and creates goodness according to its own ability, not according to what exists in the beloved. This is what the sentence above refers to when it says that the lover sees the defect of the beloved as art and the thorn as rose and jasmine.