The 51-year-old actress welcomed her son Rockwell into the world via surrogate five years ago and she admitted the youngster has had a dramatic impact on her, in every way possible.
She said: “Motherhood has completely turned my world upside down in a positive way.
“You can’t really note the changes, it’s more of an overhaul.
“Things you thought you knew, you don’t really know. The things you thought were important, really aren’t important.”
The ‘Charlie’s Angels’ star believes it’s important as a parent to find a balance between guiding her son in the right direction and allowing him the independence of making his own choices.
She added in an interview with Britain’s OK! magazine: “You have the responsibility of having another human that is 100 per cent yours.
“That human is yours to nurture, yours to love and yours to teach – but you have to allow them to have independence as well.”
Lucy has always been “career oriented” and insisted parenthood hasn’t meant that’s had to change because she now loves her work “even more” than she ever did because Rockwell makes everything brighter.
She gushed: “I love being a mother. It becomes the biggest and most important job you could ever have. I have always been very career oriented.
“After having my son, it’s not that I enjoy my job less, I love it much more because he makes everything in my life that much more.
“He helps underline everything in my life and put it all in bold.”