Kate McCann revealed that she had thoughts about being "wiped out" in a motorway crash with her family to end the pain of losing Madeleine.
But she insisted she was no longer in that state of mind, and was now "desperate" to spend time with her other children -- five-year-old twins Sean and Amelie -- and help the search for her missing daughter.
Mrs McCann also condemned the Portuguese authorities' policy of ignoring new tip-offs about Madeleine as "a farce" and said some people would be "greatly embarrassed" if she was found.
It will be three years on Monday since the little girl, then three, disappeared from her family's holiday flat in Praia da Luz in the Algarve while her parents dined with friends nearby.
Mrs McCann (42) from Leicestershire, spoke of the dark thoughts she had after Madeleine vanished. She said: "I used to have thoughts like we'll get wiped out in the car on the motorway. So it would just happen, we'd all be gone, and the pain would be away...
"But what I do know now for sure is that I don't want that. Things have changed. I am desperate to be here with Sean and Amelie and to help find Madeleine." Her husband Gerry (41) said there were people in Portugal and Britain who were trying to hamper the couple's search for their daughter.
He said: "There have been very poor elements of the Portuguese investigation, and at the same time it's probably been one of the biggest investigations ever in Portugal.
"So we aren't tarring everyone, there have been individuals who, for whatever reason, have seemingly not wanted to find Madeleine. That's how it appears to us.
"There are many people who've tried to derail what we're doing along the way."
Mrs McCann added: "I also think there'll be some people who would be greatly embarrassed if Madeleine was found and that scares me.
"That scares me. That might affect their want, or not, for Madeleine to be found."