It could also be someone else's. What happened that day, and what techniques have you developed to try to recreate that day?
I'm asking because I've been more productive these past weeks since I completely blocked out social media on my machine and I put my phone in another room during work hours, and I should have done that years ago. :(
It was amazing. I felt so alive. However, at this point, I could (somewhat tongue in cheek) credit this week with ultimately ruining my life and career. I became obsessed with recapturing that feeling, and with finding a way to support myself with my own work (as opposed to the company's work). I quit my job one year later and happily worked on my own stuff for the next 2 years. This began a pattern of living on the ramen budget, being a single hermit, only going to work when I'm broke, and quitting after a year or less. Disastrous. Why, as I write this, I haven't gone to work in over 2 years, and I'm broke again and looking for a job. I have unprofitable side-projects and repos out the wazoo though.
What makes me most productive is when I truly love what I'm working on.