get into one's head

Here, at last, I am resting from hard times at Marienbad, where the waters get into one's head, as my letter will probably show.

What fancies one does get into one’s head at a time like this!

To get into one's head what we had to look at on the upper half of the Beardmore, imagine a moderate straight slope: this is the Glacier like a giant road, white except where the sun has melted the snow and bared the blue ice.

It is quite strange what fancies get into one's head when one is—sick—heart-sick.