“It takes as much energy to wish as it does to plan.”

Relentless (1992)

Source: Irrational Man: A Study in Existential Philosophy (1958), Chapter Ten, Sartre, p. 224

The earliest appearance yet located of this statement is in 50 Ways to Lose Ten Pounds (1995) by Joan Horbiak, p. 95, where it is quoted as an anonymous proverb. It seems to have circulated as such for a few years before it began to be attributed to Saint Exupéry around 2007.
Disputed

Rawstory.com Interview (9 September 2005) http://rawstory.com/news/2005/Zinn_interview_part_two_Same_arguments_made_in_Vietnam_made_0909.html, which compares U.S. wars in Iraq and Vietnam
Context: I would encourage people to look around them in their community and find an organization that is doing something that they believe in, even if that organization has only five people, or ten people, or twenty people, or a hundred people. And to look at history and understand that when change takes place it takes place as a result of large, large numbers of people doing little things unbeknownst to one another. And that history is very important for people to not get discouraged. Because if you look at history you see the way the labor movement was able to achieve things when it stuck to its guns, when it organized, when it resisted. Black people were able to change their condition when they fought back and when they organized. Same thing with the movement against the war in Vietnam, and the women's movement. History is instructive. And what it suggests to people is that even if they do little things, if they walk on the picket line, if they join a vigil, if they write a letter to their local newspaper. Anything they do, however small, becomes part of a much, much larger sort of flow of energy. And when enough people do enough things, however small they are, then change takes place.

XI, 26, Parts of this passage has been heavily compared with later statements of René Descartes; in Latin and with a variant translations:
The City of God (early 400s)
Context: We both are, and know that we are, and delight in our being, and our knowledge of it. Moreover, in these three things no true-seeming illusion disturbs us; for we do not come into contact with these by some bodily sense, as we perceive the things outside of us of all which sensible objects it is the images resembling them, but not themselves which we perceive in the mind and hold in the memory, and which excite us to desire the objects. But, without any delusive representation of images or phantasms, I am most certain that I am, and that I know and delight in this. In respect of these truths, I am not at all afraid of the arguments of the Academicians, who say, What if you are deceived? For if I am deceived, I am. For he who is not, cannot be deceived; and if I am deceived, by this same token I am. And since I am if I am deceived, how am I deceived in believing that I am? for it is certain that I am if I am deceived. Since, therefore, I, the person deceived, should be, even if I were deceived, certainly I am not deceived in this knowledge that I am. And, consequently, neither am I deceived in knowing that I know. For, as I know that I am, so I know this also, that I know. And when I love these two things, I add to them a certain third thing, namely, my love, which is of equal moment. For neither am I deceived in this, that I love, since in those things which I love I am not deceived; though even if these were false, it would still be true that I loved false things. For how could I justly be blamed and prohibited from loving false things, if it were false that I loved them? But, since they are true and real, who doubts that when they are loved, the love of them is itself true and real? Further, as there is no one who does not wish to be happy, so there is no one who does not wish [themself] to be [into being]. For how can he be happy, if he is nothing?

Source: Kingdom Come #2 "Truth and Justice"