How did you get used to one letter variables?

I often see elegant idiomatic solutions in Clojure using one letter variables.

example 1 example 2

Is this because a lot of clojure programmers also program in haskell?

The terse variable names invariably slow down my understanding of the logic; and honestly shakes my confidence a little bit.

Are clojurians just "a cut above" and can hold way more context in their brains?

Is there anything I can do to try to get used to the terse names?