DDL .“DDL "is the abbreviation of deadline, which means deadline, and usually refers to the deadline for college students to submit their homework. And "DDL" refers to the behavior of college students trying to finish their homework in a limited time. Every final week, all kinds of final homework come one after another, and catching up with DDL has become a hot topic for college students. The common way for college students to deal with DDL is to stay up late. As the saying goes, "As long as you don't die, you will die." Many college students stay up late in the last week to catch papers and review exams, and only sleep for four or five hours every day. Although most people finally catch up with DDL, under such high-intensity study pressure, many people also feel anxious, irritable and even depressed, and their physical and mental health is seriously affected. The reason is actually very simple, that is, "procrastination." Not many college students don't understand these truths. They just don't want to do it or can't. Because under the influence of procrastination, college students will habitually pile up tasks until the end, unable to overcome psychological obstacles and plan tasks in advance. Research shows that more than 70% of college students in China have procrastination symptoms to varying degrees, and nearly 30% of them say that they often or almost always procrastinate. At the same time, most college students said that because of the delay, the progress of homework was delayed, and almost all college students said that they had the experience of staying up late to catch up with DDL. There are many reasons why procrastination is so common among college students.