If the project you were busy working on has just been shelved then you might be feeling puzzled, frustrated or even angry. Sometimes, it doesn't seem logical or even fair. It's likely that your project has suffered the consequences of one of these 3 reasons:

1. The excess of boom-times causes business leaders, in recession, to shelve projects that were once considered strategic. Why? Typically the outcome of the project is considered to add little to the core business of your organization - strengthening the core of a business emerges as the primary focus as recession takes hold. These ad-hoc projects probably still look like they create competitive advantage or disrupt your market, but in a recession it's doing the basics very well that counts. Take a look at your project and consider if its objective addresses issues at the core of the organization - operations. There is a painful truth about these projects - they were initiated by managers who were blind to the possibility that an economic downturn was ahead (or hoped that it wasn't), and then inept management didn't ensure that the cost-benefit held up even during a downturn.
2. A project will also be postponed if their outcome adds cost to operations. A project doesn't end when the Project Manager closes the gantt chart. The objectives of the project (assuming they were met) result in an effect that lives on in the business. These might be the need for extra infrastructure, extra people, more capital (money), etc. So even if a project focuses on the core business and is deliverable by affordable means it doesn't mean that it has a viable future.
3. Political shift is a major cause of projects being consigned to the dustbin. Recession creates turmoil in an organization, particularly when funding for projects is competed for and they impact the funding of operations. When the guys at the top begin to shift around, so does the context of the organization and the decision-making. Project cancellation, in these circumstances, looks completely irrational and folly, and guess what - you're right. But this happens. A classic example of this is the dismantling of the British aircraft industry since the 70s where project after project was cancelled due to political shift in the Royal Air Force and the UK government. Each project in isolation promised to deliver more capable aircraft and would have kept the UK at the forefront of military aircraft technology.