The singer/actor posted a touching tribute to his mum Katherine on 1 December (14) - the day after she died - on, and speaking at an Alzheimer's Association benefit in Los Angeles on Wednesday night (18Mar15), he admitted he's still in mourning.

He told, "Mourning is a process, and I have to take my time with it."

The 42 year old added, "The holidays were rough for me. They were really rough. You think you're OK. Even if your heart's in the right place, you still have your body. And your body knows. Your body kind of has to mourn physically as well, and that can come out in different ways. I had good friends and families and could work that out and get through that. But it wasn't easy."