Research conducted by the Center for Creative Leadership has identified a number of challenges that first-time managers (FTMs) have in common. You can read the full list here. I have chosen to focus on the top one because you could argue that the rest of the issues are all sub-issues that arise from the same overall challenge:
The FTM has been used to achieving results through a high degree of control over themselves. They set goals and manage their time and effort in such a way as to reach them. That's exactly what has drawn attention to them in the first place and is the reason they have now been promoted to their first management position.
But the way they control themselves is not going to work on others. They need to learn to switch from control to influence, which is an entirely different approach.