From this week's Parsha we read:

“Behold, I set before you today a blessing and a curse.
The blessing, that you will heed the commandments of the Lord your God, which I command you today; and the curse, if you will not heed the commandments of the Lord your God, but turn away from the way I command you this day, to follow other gods, which you did not know.”

G-d sets before each of us this choice. If we follow His Way we are blessed. If we choose not to follow His Divine counsel His blessings do not flow to us. This is the curse, to dwell without His blessings.

Our sages teach that when we have true understanding we we realize that “From the Mouth of the Most High comes neither blessings nor curses.” This is confirmed at Lamentations 3:38:

By the command of the Most High, neither good nor evil comes.

Rebbe Nachman of Breslov clarifies this for us in Likutey Moharan Book 1 Lesson 36. Because human life is dependent upon free will, what comes to humanity is more accurately conceived as 'undifferentiated light'. We receive this divine illumination in the form of luminous fibers from 'above'-- from the Merkaba or Abode of the Beloved. These neutral fibers of light are collected into vessels of our own creation. The purer our vessels the more potent the divine light is manifested outward. But if our vessels are impure, then the darkness and uncleanliness within them radiates inwardly and outwardly. Such people call evil good and good evil. Such people walk in darkness and eventually become unable to even see the Light (Psalm 82:5). Many such beings are among us today.

Let's read a bit from: Likutey Moharan Book 1 Lesson 36. We will be reading from Rabbi Israel Dov Odeser's translation, available in the three volume set from BreslovBooks.com

This can be conceived as follows: If a vessel or cup is established in the Love of G-d it receives M'aorot or 'divine luminaries', 'angels' that convey the divine essence of the letter Vav inherent in the Divine Names of Four Letters. Vav -- whose numerical value is six -- corresponds to the six emotive attributes enthusing the consciousness from chesed to yesod as conceived through the construct Adam Kadmon and the Tree of Life. The divine Vav enlivens and draws the life forces into Tiferet, the central Sefirah of Adam Kadman thus establishing harmony and balance with the Beloved. In other words, devekut.

On the other hand, without Divine Love and intent (kavanah) the Vav is missing and one experiences Mart instead of M'aorot, the curse of darkness rather than the blessings of Light, as in "M'ayrat": the curse that dwells in the houses of the wicked (Proverbs 3:33).

for the perverse is an abomination to the Lord, but His counsel is with the upright.
The curse of the Lord is in the wicked man's house, but He shall bless the dwelling of the righteous.
If [one goes] to the scoffers, he will scoff; but [if he goes] to the humble, he evokes grace.
The wise shall inherit honor, but the fools take disgrace as their portion -- Proverbs 2:32-35