Deadlines are invigorating and can provoke herculean effort into accomplishing a task on time.
However when you back yourself into a corner on a deadline, you don't have time to have problems.
If you're submitting an essay for school, you might be able to talk the teacher into accepting it late, though that might cost you some marks. It's a bad habit to get into. Ship it early.
If you're submitting a bid for a tender, lateness will disqualify you. Higher stakes, with no partial credit. Ship it early.
Deadlines decay. Any planning strategy is fundamentally about what to do in the present. Once they're in the past, they lose their power. A deadline tomorrow can cause a panic, a deadline of last week is irrelevant.
Since you can't predict future problems lock in your results early. If you send that email now, you won't be out of luck if the power goes out later. Ship it early.
Being done already eliminates unpredictable obstacles. If you're done early, you're immune to unexpected problems and you avoid the stress associated with running out of time.
Imagine this, all your deadlines are now one day earlier. Meeting that schedule won't take any additional effort, but it will come with much less stress.
This applies to big things too. Write your will before you need it. Go on adventures while your body still can. Stick to the important activities, and do them now. You're on a deadline.