Bowling is hard. At least when you bat and you are out you can hide in the pavilion, but when you bowl and are clattered for 3 boundaries in a row there is nowhere to hide. You have to finish the over.
No wonder the mind becomes cluttered with thoughts and plans when you stand at the top of the mark.
But an unfocused mind makes it difficult to bowl. How many times have you bowled wide outside the off stump, tried to compensate and end up throwing it down he leg side instead?