The 35-year-old actress and the film director parted ways in 2010 after seven years of marriage, and Kate said that she turned to the gym to make herself feel good again.
'That's the main reason I took it up... But I do feel... I don't know... part of, I suppose, my way out of everything, has been really taking care of myself,' she told Vogue.
'I think that comes from an awareness that my children really need me, and they need me to be the healthiest version of myself that I can possibly be.
'Last night I went out for a drink with two friends and, as we were walking, I said, 'God, you know, I feel so good'.
'Not in a, 'Wow! I feel so good!' way, but just in that quiet centred way. I'm almost surprised by it. I feel well, I feel healthy. I feel clear. I feel centred.'