Claire Williams revealed on Friday that she twice turned down offers to stay in her job before deciding to leave the family's Formula One team this weekend.
Williams, who will leave her position as deputy team principal after the Italian Grand Prix, said she felt she did not have the energy needed to carry on if not working for her family.
"I’ve given it my all," she said. "And I’ve done that because I wanted to protect my family’s legacy in this sport.
"I’ve done it because I’m my dad's daughter and I felt almost it was my duty to do it, so to speak.
"Now that it’s not ours, I don’t feel I could put the same amount of energy into it."
In an interview with Sky Sport F1, following Thursday’s announcement that the Williams family would sever all ties with the team after this weekend’s race at Monza and after the take-over by American investment company Dorilton Capital, she said it would have been very difficult to transfer her commitment to the new owners.
"Anyone can hope to understand that for me, working for somebody else would be potentially enormously difficult," she explained.
"I've run this team as my team for seven years and you put blood, sweat and tears into something like I have, for the time that I have, the sacrifices, doing what I've done, this is a hard, hard business.”
Williams and her father team founder Frank Williams will end their family association with the F1 team after 43 years when they walk away.
She said it had been "incredibly tough" running the team in recent years, adding it had "taken an awful lot out of me".
"If I'm honest, Dorilton needs somebody that has more energy than I've currently got, somebody that is going to put in more than I can currently give it to take it forward.
"They're going to put as much as they can into it and they're going to want somebody that can take that and really drive it forward and I don't think that I'm that person.
"I've always been very honest about my capabilities in this sport and I always thought I would know when the time would be for me to hang up my boots, so to speak, and that does feel like now.
"Dorilton wanted me, they asked me to continue. They asked before the sale was done, they asked after the sale was done, but I think a clean break is probably best all around."
She said she now felt free to pursue other areas of her life.
"It's a bit like ripping a plaster off -- you can imagine how hard this decision has been. I wanted to achieve so much more in this sport. Unfortunately, it hasn't happened for me.
"But I can go out of it knowing that I've done a few good things in this job. I haven't got everything right, by all means, but I can go out, I think, hopefully with my head held up high and I can see what else is out in the big wide world.
"And most importantly for me, I can concentrate on being a wife and a mum for a bit."