Although prolific as a sardonic aphorism, this quote is only semi-rightfully attributed to Soren Kierkegaard. And although a google search with the phrase will turn up about 100 WISDOM QUOTES! entries for Soren Kierkegaard, it wouldn't be very wise at all to take the sentiment to heart on that basis.
Actually, the phrase was taken from one of Kierkegaard's essays in Either/Or, all 'written' by pseudonymous authors that represent points of view that do not precisely correspond with Kierkegaard's beliefs. More precisely, they are meant to delineate Kierkegaard's theories about the three "stages of existence," which are distinctly hierarchical: the aesthetic, ethical, and religious. "The Rotation of Crops," is one of the essays in Either/Or part I, in which the anonymous author attempts to deal with the one great difficulty facing the Aesthetic Mode of Existence: boredom.
Kierkegaard is above all being ironic in creating a how-to guide for avoiding boredom. It is quite evident for anyone capable of reading between the lines that in attempting to avoid boredom every act in life becomes evil as a possible source of boredom. Thus, nothing must be done twice, thought about, or God forbid, remembered, or it might bore you. It is only for the aesthetic life, the lowest level of existence, that boredom is truly a problem. Consider this quote:
"This can be traced back to the very beginning of the world. The gods were bored; therefore they created human beings. Adam was bored because he was alone; therefore Eve was created. Since that moment, boredom entered the world and grew in quantity in exact proportion to the growth of population. Adam was bored alone; then Adam and Eve were bored together; then Adam and Eve and Cain and Abel were bored en famille. After that, the population of the world increased and the nations were bored en masse."
Kierkegaard is flirting with the issue. Of course everyone is affected by boredom at one time or the other, but does that mean the problem is with the world, or with us, with our mode of existence? Better yet, consider the opening, more obviously ironic, sentence:
"I begin with the principle that all men are bores. Surely no one will prove himself so great a bore as to contradict me in this."
The conclusion that Kierkegaard, not the imaginary author, wants you to come to, is that there must be a higher order to existence, in this case, the next step up is to the ethical.
One of the problems that has emerged in Kierkegaardian scholarship is how to attribute quotes like the above in footnotes. Obviously, Kierkegaard wrote them, but metaphorically they came from the mouths and minds of imaginary characters whose very names have meaning relevant to what they say. I have been avised by those who study the man professionally, to include the false name in any reference to a quote by Kierkegaard under that name. To do otherwise is begging for blatant misrepresentation of Kierkegaardian ideas, automatically out of context.