The 78-year-old actress - who is married to 46-year-old Percy Gibson - admits she can be a "total diva" and always has a specific list of demands.
She told Closer magazine: "I'm a total diva in real life. I'm very difficult - ask anybody.
"I always have my dressing room painted pink and full of Evian."
Joan also admitted she is not a fan of cosmetic surgery procedures or Botox injections and credits her own youthful looks to good skincare.
She said: "I never go to bed without taking off my make-up and applying night cream. I've been doing it for 400 years!
Joan has previously stated she believes sex is an important factor to keep looking young.
She said: "Let's not forget the importance of sex when it comes to looking and feeling good. Many of the world's most celebrated women have been sexually active well into middle age and beyond. The great French actress Sarah Bernhardt, and the legendary designer COCO CHANEL, both had lovers well into their later lives. It is every adult's prerogative to enjoy sex (although young people may not agree). It delights me to read about a couple marrying in their 80s, or discovering a lost love from 50 years ago. Romance never dies - if you believe in it."