Turning in work late doesn’t just cost points. It teaches people what to expect from you.

Handing work in late costs the marks, and that part is printed on the page. The rest is not printed. Whoever is reading it now knows something about what to expect from you, and that expectation shapes the extension you get next time, the reference they write, whether your name comes up for anything. Reputation is assembled out of small administrative facts.

Take the next deadline, work back to a date two days earlier, and treat that as the real one. Hand in something unfinished on time rather than something good late. If you are genuinely going to miss it, say so beforehand.