Don't manage work, manage time.
Don’t plan to do x number of things tomorrow, plan to do x number of things at specific times. The difference between those two is that in the former (type 1) you are managing work with no regard to the time(capacity) you have to accomplish that work whereas in the latter (type 2) where you assign a time to those things you are managing your time.
When you do the type 1 planning, you are setting wrong expectations, with yourself and/or your team with what you can deliver. Say, you have only three hours of deep work time, but you have committed to deliver 5 things that will take 5 hours(which you realize later). One of two things will happen, either you will fail to deliver or you will burn out. Instead, if you do that type 2 planning, you can look at your calendar, assess the effort it will take to deliver those 5 things and then you can commit to only doing 3 things well. When you deliver that, you are happy and the team is happy.
Manage your time, fit the work in that. Time is the constant(24 hours), the amount of work you take on can change.
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