After nine years with Scott Disick, Kourtney Kardashian called it quits on their relationship – and now Disick's friends are worried that "there's no real incentive for him to get himself together," a source close to the 32-year-old tells PEOPLE.
"When he's gone to rehab or sought treatment for his issues, it has been after an ultimatum: Get treatment or it's over," the source says. "If it's over, there's no real incentive for him to get himself together."
Earlier this year, Disick's struggle with substance abuse led him to check into rehab, as seen on Keeping Up with the Kardashians.
"Scott insisted that his drinking is under control, that he's not in a spiral, but everyone around him knows the truth," says the source. "He has been lying to everyone, saying that he's clean and sober ... and he insists that he doesn't have a problem."
Scott Disick Posts Birthday Message to Daughter After Split from Kourtney Kardashian
On Monday, news broke that the longtime couple – who are parents to Mason, 5, Penelope, 3, and Reign, 6 months – had split after Disick was photographed getting cozy with Los Angeles-based stylist Chloe Bartoli in Monte Carlo.
"She was over dealing with his constant lies and addictions," another insider told PEOPLE about Kardashian, 36. "It was becoming a poor environment for the kids to be raised in, and she refused to let that be the case."
"Kourtney is willing to sacrifice her relationship with Scott in order to keep [her kids] safe," the insider adds. "Her children are her first priority. She needs to protect herself and her family, so she knows this is the right decision."
For more on Kourtney and Scott's split, pick up this week's issue of PEOPLE, on newsstands Friday