Is it true that actors or future actors face anxiety or stage fright during acting classes or auditions?

Stage Fright is common among Actors and us non-acting folks.
These noted performers (and many more) have publicly discussed their stage fright:
  • Barbara Streisand
  • Megan Fox
  • Jonathan Knight (New Kids on the block)
  • Brian Wilson (the Beach boys)
  • Annie Lenox
  • Adele
  • Ella Fitzgerald
  • Stephen Frye
  • Carly Simon
  • Cher
  • Fiona Apple
  • Sir Laurence Olivier

Acting classes and extensive public speaking help get past Stage Fright.  While many performers indulge in meditation, alcohol, massage, etc.,  Sometimes they need to perform enough to relax in front of their fans.  Performance anxiety, like forgetting lines, creates and sometimes increases stage fright and the “jitters”.
Performance Anxiety Cure: How To Overcome Performance Anxiety And Stage Fright In All Aspects Of Life Forever (anxiety recovery, panic attacks, anxiety management, anxiety attacks) by [Underhill, Larry]
When you get “into character”, you have license to be someone other than yourself, and that often gives us – as performers –  the ability to be that person, without stage fright or exposing our personal anxieties.
Before an audition, practice relaxation exercises, learn your script really well, and “break a leg”.
Thanks for reading my point of view!
The Last Word:

Is an actors’ public persona reliable? Authentic?

Alan Chenkin, Learned about celebrities reading magazines at the supermarket checkout
“We are each responsible for our own life – no other person is or even can be.” – Oprah Winfrey.
Most actors have a public and a private persona. The public persona is their brand, how they show themselves to the world, and how they get more roles, recognition, and exposure. Good actors have a consistent and reliable brand, so endorsement deals, roles, and commercial work can have their consistent star power on their packaging. An actors private persona is when the paparazzi have gone, they are at home or in repose, and they are not “performing” or being in character.  Having a “private” persona means they can rent hotel rooms, cars, and charge meals without revealing their true identities.  It allows them to have a life outside their famous identity.
From the Web:
A professional actor will have a consistent  brand.  They will be in character, have measured behaviors (as their fans come to expect), and deliver reliable performances and numerous public relations work (appearances) for their studios/TV/Stage gigs.  Promotion is an important part of the business, and most professional actors have a team of people managing their social media, Paparazzi, and public relations.
When you see an unreliable actor or Diva, you have to wonder if that is their public persona, a publicity stunt, or are they cracking under pressure?  For Example, Tom Cruise excitedly jumped up and down on the Oprah set.  It was unexpected, and got a lot of press for the actor.  
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Expanded and edited from my answer to this question on Quora.