As a project leader, your role number one is to communicate the project vision. This is more important than ever as project resources typically work across many projects every day. With a clear vision and outcome, it is easier to know the right action and decision at each junction.
Vision is also connected to purpose and hope, as "without vision, people will perish". I particularly like this quote from a church in Wessex: "Vision alone is but a dream. Task alone is drudgery. Vision and task together gives hope."
If you're working on a project where the vision isn't clear, then the most important next task is to find that vision.