Shirra's first flight followed the near disastrous Carpenter flight: he said he would save as much fuel as possible and drift as much as he had to. He flew 6 orbits (9 hours) and saved more fuel than Glenn or Carpenter did, who flew 3 orbits.
Then, for Gemini 6, he save the day by not ejecting from the cabin when the rocket wouldn't lift off. He flew to Gemini 7 , very close to it and returned back. it lasted just 24 hours.
But when Apollo 7 was meant for him, he jst applied his big principle: do just what you have przpared for, and nothing else.
He left no room for improvisation, changes, adaptation. And the Apollo spacecraft was perhaps too big for his attitude, indeed.

Raoul