I don’t know that it’s universal, but the lightbulb is a powerful symbol for making a connection. One second you don’t know something important, the next you do.
I remember being sat on a train in early 2005, less than six months into my PhD. I was waiting to go and visit a friend. Just as the train doors were closing something CLICKED in my head and I could see the answer to a problem. It was just a little one but one at the root of a bigger problem in my thesis. Just like that, it came to me. And while there was a lot more work to do, this one little insight allowed me to write three chapters of my thesis. There were harder problems in my PhD, but this is the time I remember when something just came to me. Weeks of reading, of doodling and noodling, and then CLICK.
When you have a real lightbulb moment, be grateful.
What else are you grateful for in your PhD?