Always plan for surprises. Add allowances to the schedule.
Need to renew documents? Don't push it 'til expiration date. Systems might be down and unable to process transactions. Typhoons may cause offices to close. You might not reach the cut-off for the day because of too many people cramming renewals like you are.
Going for a trip? Pack early, not a few hours before your flight. You might be missing a few items and have no time to buy them. You might find out that your bag's zipper is broken. Or that all your good clothes need to be washed. Or that you've misplaced many of the things you need to bring, and now have to rush around looking for them.
Planning a huge project and needing to promise a completion date? Add a buffer in there—like two weeks or two months. You might miss including a couple of steps during planning and find out in the middle of the execution. Or an urgent matter might arise causing you to step back for a few days.
Whatever it is you're doing, there will always be surprises.
Plan for them by always having allowances.