"Some of us put ourselves out there and do this," she said, her voice breaking and her eyes glistening with tears, "against some pretty difficult odds and we do it, each one of us, because we care about our country."
"But some of us are right and some of us are wrong," she said in a quaking voice. "Some of us are ready and some of us are not."
Voting in New Hampshire ends at 8 p.m. EST on Tuesday, with results expected to begin rolling in quickly.
Clinton, a New York senator who would be the first woman U.S. president, promised to stay in the fight until it was over, possibly on "Super Tuesday" on Feb. 5, when 22 states hold nominating contests.
Video: New Hampshire, Your Money, Your Vote