I hated being late to school because I'd have to go the attendance office for a tardy slip – and too many tardies might mean a detention.
You may not get a detention as an adult for being tardy, but you can get fired from your job if it happens often enough. Even if it doesn't reach that point, being late makes you look disorganized and unprofessional. In private life, your friends and family can get resentful really quickly if you're always the last one to arrive to a gathering, or if you miss the big moment at events.
Tardiness may stem from a lack of self-motivation or from an overscheduled life. Additionally, some people actually get an adrenaline high from keeping others waiting. Others are just overly optimistic about how long it really takes to get from Point A to Point B [source: Schocker].
But you can become more punctual if you work at it. First, stop trusting your internal clock. Actually time how long it takes to get you to work, for example, including rush-hour traffic, as well as the time to walk from your car to your office building to your suite. If you're a very busy person, or get so wrapped up in one thing that you easily forget about other commitments, set appointment reminders on your smartphone or laptop and be sure to schedule some down time during the day.