Priorities are proved by calendars, not by intentions.
Open yours and look at what has a block drawn round it. The meetings are there. The dentist is there. Somebody else's deadline is there in bold.
The hour that would actually settle you is almost never written down anywhere, which is exactly how it becomes the first casualty when Thursday gets crowded. Unbooked time is not protected time. It is simply available to whoever asks.
None of that requires a life overhaul. It requires one thing in the diary with your name against it that other people are not allowed to take.