For me it isn't about maintaining my own schedule it is about managing the expectations of others, be they managers or colleagues. I have "office hours" on my calendar where people can book in with me and then the last couple of hours of my day people know I'm interruptible. Outside of those hours I don't check email, don't have any chat open and my phone goes straight to voicemail with a message to call me again if it is an emergency, which will make it ring. I start work very early (05:30-06:00) and am most productive in the mornings, so my office hours and interruptible time is when I'm starting to wind down and my capacity for deep work is reducing.