Life changing in that it changed my professional life. Steve Yegge's piece that all programmers are typists, http://steve-yegge.blogspot.com/2008/09/programmings-dirties.... It's been a while since I read it but my recollection of it is that your tools matter and that you need to practice to get good in using your tools. Prior to reading this I was so focused on solving "the problem" that I never realized that I spent a lot of mental energy on the tools rather that was much better spent on solving whatever I worked on. This realization has changed how I approach technical stuff in my day-to-day job.
