Article continues below advertisementKate Middleton has been praised for her serene public composure since returning to royal life, but behind the scenes, her recovery from cancer has been far more punishing than appearances suggest, according to sources who tell OK! the process has been physically and emotionally exacting.The Princess of Wales, 44, pulled out of attending the second day of Royal Ascot on June 18, despite being listed in the official carriage procession alongside her husband, Prince William, 43.