Catherine Zeta-Jones reportedly worries she and Michael Douglas haven't "truly dealt" with their issues.
The couple have been married for 13 years and have children Dylan and Carys together.
Last year they confirmed they were on a trial separation, which came after a tough few years including Michael's throat cancer in 2010 and Catherine's rehab treatment for bipolar.
While they are trying to get their marriage back on track the 44-year-old actress allegedly fears there are still troubles left unsolved.
"Catherine's thrilled that they're giving their romance another shot, but she worries that they haven't truly dealt with their problems," a source told British magazine Closer.
On top of this Catherine is said to be scared Michael will leave her if times get difficult again. She reportedly feels guilty for her illness affecting their relationship.
"She thinks her bipolar played a big part in their separation. She's told pals she fears that if it flares up again or they have to endure something more difficult, it will prove too much for Michael and he'll leave," the insider added.
"However, he's reassured her that he's committed to working at the relationship."
Amid the turbulent period the 69-year-old actor is still making sure to give focus to his kids. It was recently reported he cooks breakfast for them every day, despite having lived apart from his family.
“When he’s in New York, he makes the kids breakfast and comes back in the evening to watch TV with them before bedtime,” a source told British newspaper The Mirror.
“Then he gets his marching orders from his wife and returns to sleep at his own place in Manhattan.”