Check your physical health. An injury (and failed surgery) obstructed my breathing. Big impact on my ability to get into and maintain "flow". Sleep apnea (no

Check your physical health. An injury (and failed surgery) obstructed my breathing. Big impact on my ability to get into and maintain "flow". Sleep apnea (not something I've been diagnosed with, although...) is often cited as a problem in this vein. Some people become so used to its chronic presence that they don't realize just how tired and impacted they are.