A student of mine recently completed first solo. Being of the restricted ilk a friend of mine sent him off for the big occasion.
Upon landing and vacating the runway the tower controller offered his hearty congratulations etc to which bloggs replied "thanks, I was f**king !!!!!t*ng myself".
I think the call it release of nervous tension or something like that.
He wasn't !!!!!t*ng himself at the end of second solo so we are making progress!