I tracked my screen time and my Working Δ daily for 60 days. The single strongest predictor of a good practice session was whether I had used my phone in the first hour after waking.
Days where I went phone-free for the first hour: average Working Δ session score +3.2 above my mean.
Days where I checked my phone within 15 minutes of waking: average session score -2.1 below my mean.
The effect is large enough to be visible in a 60-day sample. The mechanism is presumably attentional — starting the day in reactive mode (scrolling, responding) versus deliberate mode (reading, planning, practicing) sets the baseline for the rest of the day.
Sunlight before screens. The institution prescribes this. The data supports it.