In a letter to his "shallow, reckless, cocky younger self," to celebrate his upcoming 50th birthday on October 7, Simon revealed he suffers from "black moods."
"Sometimes, when friends are over, you want to ask them to leave. You get hit by black moods and you want to be alone," he writes in the letter, printed in the U.K.'s Daily Mail on Monday.
Simon addresses the success and failures of his younger years in the lengthy note, but his revelations on his life now and the lessons he has learned, provide insight into the famed judge's personal life.
Among the revelations? Simon wrote he has "no regrets" about being a bachelor at 50.
"You never married, but you have no regrets about that," he wrote. "Family life would be a problem now. You almost never stop working, or thinking about work."
And a lesson many learned during the current global financial crisis, but one Simon learned years ago when he lost everything, "Carrying a debt is a much bigger burden than having nothing."
Another tidbit Simon gleaned from his 50 years? "Friendship is important," he wrote, noting he is still close friends with three of his ex-girlfriends.
Despite a report in the U.K.'s Mirror over the weekend that Simon is negotiating a deal worth $103 million to bring his "X-Factor" television show to America, Simon revealed he remains insecure about being on television.
"Sometimes you wonder how much longer you will stay on television because you don't ever want to be unwelcome," he wrote. "In life, you have always insisted that you had an invitation to the party and you feel the same way about being on TV. You need to feel you are welcome into people's homes, not somehow forcing your way in. If you feel that is happening, you will be off, gone."
To read all of Simon's lengthy letter, click HERE.