In today's face-paced work environment, decisions and requests for action are bombarding you constantly. If you make these decisions in "firefighting" reactionary mode, you are more likely to make mistakes.
Faced with a large new assignment and no experience of working on this type of activity or anything this large, it is easy to lose confidence. As you move forward and hit roadblocks or potential risks become reality, you may be ready to quit.
Project management is the art and science of getting results by following a roadmap laid down to turn customers' desires into concrete products and services by following established procedures in a defined sequence.