Neil's Hubby On Wagon!

Hard-partying sitcom star David Burtka has said goodbye to booze!

"It just didn't mix well with me anymore," reveals the How I Met Your Mother actor.

David, 42 did it for Gideon and Harper, his six-year-old twins with husband Neil Patrick Harris: "I thought, 'You know what? I owe it to myself. I owe it to my kids, to be there, 100 percent.' "

He says it won't be easy: "I'm not one of those people that can just have one drink or two drinks."