Actor Matthew McConaughey.Getty Images

Kay McConaughey claims the 'Interstellar' actor is the same happy-go-lucky guy he's always been and hasn't changed since carving out a career in Hollywood.

She said: "As long as I can remember, he's been happy. He's the same thoughtful, kind, happy person he always was. He's just Matthew."

The 45-year-old actor was devastated by the death of his father, Jim, in 1992, but it helped him see the world differently.

He said: "A boy loses his father, he quickly becomes a man. I was 22. I remember clearly the sobriety I felt in the pain of my father passing. The sorrow refined me, and I never looked at the world the same again.

"Everything I previously revered and looked up to suddenly dropped to eye level and felt more mortal and attainable, while everything I patronized and looked down upon rose up to a more respectful eye level and wasn't beneath me. The world was suddenly flat, and I looked it square in the eye with more courage and incentive than ever before."

The Hollywood hunk decided to start pursing more challenging roles after working on the 'Lincoln Lawyer' in 2010, as he wanted to seek out better "personal experiences."

He added to PEOPLE magazine: "I ask myself before making a choice, 'What experience am I going to have in this?' I give less of a damn about the result."