Former Secretary of State Hillary ClintonHillary Diane Rodham ClintonKoch brothers group won't back Stewart in Virginia Giuliani says his demand for Mueller probe to be suspended was for show Poll: GOP challenger narrowly leads Heitkamp in North Dakota MORE said she felt she had “let people down” with her failed run in 2008, and admitted that she “didn’t have a very good strategy” for her bid.

But she pledged, if she runs in 2016, to be “working as hard as any underdog” because even as the prohibitive frontrunner for the Democratic nominee, “I don’t want to take anything for granted.”

In a wide-ranging interview with ABC news, Clinton gave no further hints as to her decision on what’s widely expected to be another bid for president in 2016. But she did offer some insight into what went wrong in 2008, and the issues that are factoring into her choice.

“It was personally painful, [I had a] sense of real loss and disappointment,” Clinton said of her loss in the 2008 Democratic presidential primary to President Obama.

“And I did feel like I had let people down, honestly a lot of women and girls who had invested their hopes in me, but men and boys as well, across the country,” she added.

But Clinton said the loss didn’t cause her any depression, “just a deep regret.” And hinting at what she might do differently this time around, Clinton said she felt she lost “because I really didn’t have a good strategy for my campaign.”

“I didn’t plan it the right way. As a candidate who is already so well-known, I don't think I ever said, ‘Yes, you may have known me for 8 years, but I don’t take anything for granted. I have to earn your support,” Clinton said.

She said her campaign really got into gear after her loss in Iowa, but by then it was too late.

Looking back, Clinton said she was not “effective” at calling at sexism from her opponents, who often fixated on her outfits rather than her policy positions.

“I was not as effective calling it out during that campaign either,” she said, “because there is a double standard, we live with a double-standard, and people ought to think about their own daughters, their own sisters, their own mothers when they make comments about women in public life.”

“When you’re in the spotlight as a woman, you know you’re being judged constantly. I mean it’s never-ending,” Clinton later added.

She has learned, since 2008, to “not worry so much about what other people are thinking.”

“I’m going to say what I know, what I believe, and let the chips fall,” Clinton said.

The former secretary of State is the prohibitive frontrunner in the race, with nearly every poll of the Democratic field showing her taking more than two-thirds of the vote.

An ABC News/Washington Post survey out this weekend gave her 69 percent of the vote, with Vice President Joe Biden in a distant second with 12 percent support.

She said she will “probably likely” make the decision whether to run next year, but that she doesn’t think her deliberations have frozen the field.

“People can do whatever they choose to do, on whatever timetable they decide,” she said.

Clinton dismissed concerns over her health, her age and comments from Barbara Bush that were critical of the prospect of another Clinton-Bush matchup, in light of the possibility of former Florida Gov. Jeb Bush.

The strongest reason to say no, Clinton said, is “because I really like my life,” with a grandchild on the way and a lucrative career on the speaking circuit.

But if she does run, Clinton said she’ll be “working as hard as any underdog or any newcomer.

“I don’t want to take anything for granted if I decide to do it.”