If you need proof..
.. as previously suggested, Gann's "Fate is the Hunter" is a must-read..Night-time DC2 heavily laden with ice... long periods among the mountains and valleys at max power yet still teetering at the stall... diversions and alternate closed out by wx and getting mighty low on fuel.
We (hopefully) learn plenty from ATPL ground-studies.. but Gann was a wonderful wordsmith.. and his various encounters with CBs are printed in my soul. RIP EKG