Complete part of the project - Do a stakeholder analysis, can part of the project be completed and satisfy key stakeholders. Get customer to recommend - Shows the importance of including your customer from the start. Requirements Definition - make it available to other projects and departments. The need for an orderly close out is especially required when canceling a project. Hopefully, your organization has a formal checklist.
Documentation is a company asset.
Key learnings and their dissemination, with the support of senior management, will reduce the probability of repeating actions that did not work. The last is the toughest, there is usually little enthusiasm for follow up.