The 47-year-old actor had fans worried about his sobriety after TMZ obtained video of him stumbling after attending the UNICEF Masquerade Ball in West Hollywood on Saturday night. As a source tells ET, "Sobriety is difficult for anyone struggling with addiction. Ben has been honest about his recovery and takes it day by day."
"He never said he wouldn’t slip up," the source adds.
Affleck referenced his recovery just hours before the party. In an Instagram post that also poked fun at reports he's using the exclusive dating app Raya, the father of three wrote: "HA, you got me. I’m dating. But let’s be serious for a moment and talk about something that is actually important. I have been in recovery for over a year and part of that is helping out others."
"@themidnightmission is an incredible organization that helps those in need with housing, training, development and recovery," he continued. "I’m making a donation today because there are people battling addiction every day that don’t have the resources and need help. @raya, you in? Who else is with me? Click the link in my bio to donate."
Concerns about Affleck's sobriety come one year after he completed a 40-day stay at a treatment center for alcohol addiction in Malibu, California, last October; he was driven to rehab by his ex-wife, Jennifer Garner.
On Sunday morning, hours after the masquerade event, Affleck was reportedly spotted arriving at Garner's house.
"You could tell that it wasn’t an easy thing for him, but Ben owned his mistake," a source told People magazine. "He said it happens, that he slipped up but that it won’t happen again. It was a smart move because now the story is basically over."
The source added that Affleck "looked tired."
A source told ET in August that Affleck -- who has been open about his years-long struggle with alcoholism -- was working to stay dedicated to his sobriety. "He's still in the program. He knows the importance of making his sobriety a priority while planning his next step in life," the source said.
"He's in a better place in his life and recovery," the source continued. "He wants to be the best he can be. He can come home at night and hear his own thoughts. Those closest to him are proud of his progress."