Simon Cowell likes to be on his own when he gets down, according to Louis Walsh.
The 'X Factor' UK judge has revealed his boss has "dark days" like everyone else, but the media mogul prefers to spend time alone when he gets in bad moods.
He told the Daily Mail Weekend magazine: "Yes, he's human and he has dark days like everybody else.
"I don't see him when he's like that; he goes off and keeps to himself."
Although the music manager might not see much of his friend during those moments, he insisted the pair are very close and have an understanding based on trust and "honesty".
He said: "Simon loves honesty. I'm always critical of him, and he's always slagging me off.
"That's why we get on so well. We're very loyal to each other, which is important."
Louis also spoke about the 54-year-old star's relationship with his pregnant lover Lauren Silverman, and insisted their son will be great for Simon, who he describes as "a big child".
He added: "There's a spark between them that I hadn't seen with him and anyone else.
"They're like teenagers in love, having fun. She lights up when he's with her.
"Simon's a big child himself, so I think the boy they're expecting is going to be brilliant for him. He seems happier."