“There's no hope, but I may be wrong.”

As quoted in The West : Who is the Savage? (2001) PBS http://www.pbs.org/weta/thewest/program/episodes/four/whois.htm
Context: Although wrongs have been done to me I live in hopes. I have not got two hearts. … Now we are together again to make peace. My shame is as big as the earth, although I will do what my friends advise me to do. I once thought that I was the only man who persevered to be the friend of the white man, but since they have come and cleaned out our lodges, horses, and everything else, it is hard for me to believe the white man anymore.

Source: Brother Odd

When asked asked if he was willing to die for his beliefs.
The Times book of quotations (2000), p. 84
Disputed
Variant: "I would never die for my beliefs because I might be wrong."

To Lord Coleridge, in response to the question, "Have you no doubts about it, Jessel?", asked with regard to Jessel's judgment as to the Alabama claims. When later asked about the truth of the story, Jessel replied, "very likely, but Coleridge with his Constitutional inaccuracy has told it wrong. I can never have said 'often wrong'". Reported in Robert Q. Kelly and Frederic D. Donnelly, The Law Library: Proceedings, Sixth Biennial A.A.L.L. Institute for Law Librarians (1964) p. 51.

As quoted when he talked about his piano concerto, op.11.
Context: Here you doubtless observe my tendency to do wrong against my will. As something has involuntarily crept into my head through my eyes, I love to indulge it, even though it may be all wrong.

Speech http://hansard.millbanksystems.com/commons/1865/feb/27/adjourned-debate-resumed in the House of Commons (27 February 1865). The origin of the famous epigram, "Tenant right is landlord wrong."
1860s

Conclusion
1880s, Personal Memoirs of General U. S. Grant (1885)
Context: I feel that we are on the eve of a new era, when there is to be great harmony between the Federal and Confederate. I cannot stay to be a living witness to the correctness of this prophecy; but I feel it within me that it is to be so. The universally kind feeling expressed for me at a time when it was supposed that each day would prove my last, seemed to me the beginning of the answer to "Let us have peace."
The expression of these kindly feelings were not restricted to a section of the country, nor to a division of the people. They came from individual citizens of all nationalities; from all denominations — the Protestant, the Catholic, and the Jew; and from the various societies of the land — scientific, educational, religious or otherwise. Politics did not enter into the matter at all.
I am not egotist enough to suppose all this significance should be given because I was the object of it. But the war between the States was a very bloody and a very costly war. One side or the other had to yield principles they deemed dearer than life before it could be brought to an end. I commanded the whole of the mighty host engaged on the victorious side. I was, no matter whether deservedly so or not, a representative of that side of the controversy. It is a significant and gratifying fact that Confederates should have joined heartily in this spontaneous move. I hope the good feeling inaugurated may continue to the end.