"I'm not disappointed. I'm not heartbroken," Palin, the eldest daughter of former Alaska Gov. Sarah Palin, told Leno on NBC's "Tonight Show" Friday.
"I tried to make it work for my son. It didn't work, and I realized that we're not meant to be, and I'm just focused on being a good mom," Palin said.
Leno asked Palin about Johnston's purported plans to run for mayor of Wasilla -- where Sarah Palin was mayor from 1996 to 2002.
"He needs to move to Wasilla, to the city limits, and he needs to get his GED," Bristol Palin responded with a laugh.
She told Leno rehearsals for her upcoming stint on ABC's "Dancing With The Stars" are no joke.
"We've had three days of rehearsals. I expected it to be hard work, but I'm so uncoordinated and don't have any rhythm so we're starting from scratch," she said.
Celebrity Families of 2014 [PHOTOS]