Macroeconomics

I think I finally get macroeconomics and what causes recessions (at least some inkling).  Recessions exist because of resource pressures.  Take a decrease in the supply of oil, for instance.  This leads to more competition over those resources by businesses which use oil.  These businesses must pass down their costs by downsizing employees or by being pushed out of business (or raising prices, which pushes the economic problem to consumers, just as oil price increases affected this business in question).  In either case, some of the value of the work done by that company is no longer a resource in that economy.  This lowered value is passed down by the employees not spending money as before.  These positive-feedback forces are somewhat mitigated by savings (personal and otherwise) and loans.  But savings and loans are mitigated by the chance of default which can be a hindrance if banks are overconfident (in the safety of their loans).  This, because it is so interconnected, is what happens when banks collapse.