The Democratic candidate said she had wanted to "curl up with a good book and never leave the house again".
But in a speech at a children's charity she urged the audience to fight for American values and "never give up."
Mrs Clinton won the popular vote but was beaten to the presidency in the all-important US electoral college.
"Now I will admit coming here tonight wasn't the easiest thing for me," she said as she was honoured by the Children's Defense Fund.
She continued: "I know many of you are deeply disappointed about the results of the election. I am, too, more than I can ever express.
"I know this isn't easy. I know that over the past week a lot of people have asked themselves whether America is the country we thought it was.