I don't think I've ever felt nervousness or anxiety when airborne, only pre-flight.
Even in situations which, looking back, might have turned out badly (severe engine problems, extreme turbulence such as one can no longer control the aeroplane) I find the emergency concentrates the mind to the task in hand - no free brain capacity for nerves! And of course the much-practiced training kicks in so some things are 'Pavlov Dog' automatic (such as stick forward on power loss).