I sometimes have that feeling....usually when the weather is the best....the sector is a very long one...plenty of fuel...everything is absolutely hunky-dory.....then one has time to think, contemplate one's choice in occupations. What brings this on....beats me. I always wondered what it would be like to sling a blade....would it depart at the five o'clock position or somewhere else....I think I settled on the eleven o'clock direction for some reason.
On the other hand....when the weather is like that Chinese Indian girl....Ug Lee.....fuel is an issue....turbulence is banging you about....temp is running just below freezing...and it is raining yet.....I do not seem to get those uneasy feelings.
I see the difference being having the time to think about things that should not be thought of while flying....those are best left to other times. Bottom line, if you have these thoughts you are only getting in touch with your own mortality....it is a risky business we are in. I buy lottery tickets too....hopefully I will win that one before my number comes in on the other.