“Change is never easy, but always possible.”

Not a Kerouac quote, but by Jon Krakauer, from his nonfiction book Into the Wild (1996).
Misattributed
Source: On the Road

Source: It

Amazon.com Interview: Larry Wall http://www.amazon.com/gp/feature.html?ie=UTF8&docId=7137.
Other

As quoted in "Archbishop urges battle with racism" http://articles.chicagotribune.com/2002-02-18/news/0202180155_1_racism-archbishop-desmond-tutu-st-sabina (18 February 2002), by Sabrina L. Miller, Chicago Tribune, Illinois

Source: The Monkey Grammarian (1974), Ch. 4
Context: My phrase is a moment, the moment of fixity in the monologue of Zeno the Eleatic and Huí Shih (“I leave today for Yüeh and I arrive yesterday”). In this monologue one of the terms finally devours the other: either motionlessness is merely a state of movement (as in my phrase), or else movement is only an illusion of motionlessness (as among the Hindus). Therefore we ought not to say either always or never, but almost always or almost never, merely from time to time or more than is generally supposed and less than this expression might indicate, frequently or seldom, consistently or occasionally, we don’t have at our disposal sufficient data to state with certainty whether it is periodic or irregular: fixity (always, never, almost always, almost never, etc.) is momentary (always, never, almost always, almost never, etc.) fixity (always, never, almost always, almost never, etc.) is momentary (always, never, almost always, almost never, etc.) fixity…. All this means that fixity never is entirely fixity and that it is always a moment of change. Fixity is always momentary.

"Dreams"; first released as a single (29 September 1992)
Everybody Else Is Doing It, So Why Can't We? (1993)

[199709041935.MAA27136@wall.org, 1997]
Usenet postings, 1997

On the BBC Radio 4 series Politics in the Seventies (10 June 1973), quoted in The Times (11 June 1973), p. 3
1970s