Work vs. Writing

I just got out of work a few minutes ago and feel like my brain is non functional. I tried to work on writing, but for some reason I never can after my work day. I can write as much as I want when I'm done working, and I'm pretty sure I could finish writing an entire novel if given the chance to write at work (which is why I keep a notebook with me at all times). Today I encountered someone who I thought was a great inspiration for a minor character in a grim reaper story that I'm writing. In the grim reaper story, my main character hates her job. I thought it would be awesome to write about the different types of characters she runs into, which means drawing from some of my own experiences. I thought it would be easy to just sit down and write a few paragraphs after work, but I was wrong. I'm not sure why, but it's like working drains all my energy. I might have to start taking naps after work so that I can write.