Getting started in the role of project manager is not always easy. Are there some common mistakes that you see newer project managers making that can be avoided (e.g. trying to on too much themselves, allowing problems to linger too long before addressing them)?

Getting started in the role of project manager is not always easy. Are there some common mistakes that you see newer project managers making that can be avoided (e.g. trying to take on too much themselves, or allowing problems to linger too long before addressing them)?