Overconfidence can affect anyone—even you.
When we have a tight deadline, most of us can finish a lot of work quickly. But if the deadline is far away, that same work takes much longer. Why is that?
It's called Parkinson's law: "work expands so as to fill the time available for its completion."
Have you ever met a manager who wasn't good at their job? There's a good chance that that person was a very good team member before they got promoted. But, the skills required in lower-level jobs don't always translate to upper-level jobs.