You may find that you are able to make changes fairly easily. A chronically late client, who had made only limited progress after many discussions of this issue in therapy, became significantly more punctual after reading this site. Realizing that other people shared his problems and that it is possible to make changes made him less ashamed and more motivated to make efforts to be on time. Quoting Oprah quoting Maya Angelou he explained: “When you know better you do better.”
On the other hand, if you find that change is slow in coming, remember that it takes repetition to create and strengthen new, punctuality-promoting emotional associations and ways of thinking that can supersede the old, lateness-producing ones.
Becoming more emotionally self-aware, developing self-discipline and an ability to delay gratification, coming to terms with your own limitations and the imperfections of the world, addressing attentional or self-esteem issues, changing your understanding and expectations of interpersonal relationships may all be involved in the process of becoming more punctual. These are fundamental changes that won’t happen overnight. You might need help to achieve them, whether it be reading books or working with a mental health professional. (I strongly recommend Kelly McGonigal’s The Willpower Instinct for dealing with self-discipline issues.) Ultimately, making these changes will improve your life in ways that go well beyond being on time.