Being ungrateful for a blessing causes it to be taken away.

A worship that can be conducted by persons who refuse to give shelter to the houseless, to give bread to the hungry, clothing to the naked, and who enjoin obedience to a law forbidding these acts of mercy, is a curse, not a blessing to mankind.

Well, what is a blessing but a curse from another point of view?

There are many good people who are denied the supreme blessing of children, and for these we have the respect and sympathy always due to those who, from no fault of their own, are denied any of the other great blessings of life. But the man or woman who deliberately foregoes these blessings, whether from viciousness, coldness, shallow-heartedness, self-indulgence, or mere failure to appreciate aright the difference between the all-important and the unimportant — why, such a creature merits contempt as hearty as any visited upon the soldier who runs away in battle, or upon the man who refuses to work for the support of those dependent upon him, and who though able-bodied is yet content to eat in idleness the bread which others provide.

Now a curse upon Because and his kin!

Nothing great enters the life of mortals without a curse.

The boon and benevolence which is not thanked for, is like the sin which is not forgiven.

Knowing’s a blessing, relaying it is the curse.

Self-contemplation is a curse
That makes an old confusion worse.

It’s like having to make a choice: a blessing or a curse. The one thing you can’t do is choose neither.

All blessings do not bless the same.

Love can be a terrible curse, Eragon. It can make you overlook even the largest flaws in a person's behavior.

You will be required to do wrong no matter where you go. It is the basic condition of life, to be required to violate your own identity. At some time, every creature which lives must do so. It is the ultimate shadow, the defeat of creation; this is the curse at work, the curse that feeds on all life. Everywhere in the universe.

If you forget to come back for Madame Zeroni, you and your family will be cursed for always and eternity.