You should be a generalist, interested to look left and right, focused on the overall target, and not getting lost in detail. Good technical understanding, commercial attitude, basics contractual/legal understanding and target driven.
I would say the complexity and the lack of time. A lot of work has to be started based on preliminary assumptions. If you wait for the final design you are not able to meet the deadlines. You have to deal with a lot of ad-hoc issues and be able to make decisions even if you lack some information.
Typically, TGE projects are unique. We are selected when a project is too complicated or too specific for our competitors. At TGE, the project manager still manages and leads the project, not just administrates it as in many larger organizations.
I really enjoyed working in Hamina, Finland. Reasonable and unagitated way of doing business and incredibly beautiful landscape.