In early American, a sheriff or constable or other community members would serve as executioners. There weren't enough executions to require a full-time executioner. In England it was a hereditary position. I only know of two first person accounts by executioners during the early modern period; one is English and it's an apology written by "John Catch" (a probable pseudonym as many English executioners are referred to as John Catch in literature). There's also a journal by a German executioner that details his torture and killing techniques. It's gruesome and one of a kind. I'm on my phone but I'll post a link if I find it when I get to my computer. The German is a methodical and cold killer.

Edit: The German Executioner is Franz Schmidt. Here's a link to more info: http://www.americanacademy.de/home/program/past/gods-executioner-meister-franz-schmidt-nuremberg-ca1555-1634

Because professional executioners still exist, it may be a good question for /r/askpsychology/ or even /r/askscience , potentially. I've read a couple of studies on this topic, all based on pretty recent evaluations.

It might interest you to read about Vassily Blohkin, a Soviet executioner that killed thousands of people by his own hand. He was handpicked by Stalin, most likely for his cold demeanor and complete lack of remorse. http://rarehistoricalphotos.com/vasili-blokhin-historys-prolific-executioner/

There's also an interview with the official Saudi beheader somewhere in youtube.