Separate fixed commitments from preferences
Start with the things that have a set time or affect other people. Then note the tasks you would like to do when there is room. Keeping the two distinct can make it easier to see what is flexible.
Estimate time with your actual circumstances in mind, including travel, preparation and interruptions. A list that looks shorter on paper may be more realistic and more useful.
Choose a next step
A large task often needs a small, concrete starting point: finding a document, sending a question or putting the materials in one place. Write down that next step rather than expecting the whole task to fit into a single instruction.
Leave gaps between activities where possible. An unfilled part of the calendar can accommodate delays or simply remain open. There is no need to justify every interval with another productive activity.
Revise without starting over
When something changes, adjust the relevant part of the plan. Carry forward what still matters and remove what no longer does. A plan is a working note for your day, not a record of whether you managed to predict it correctly.