Recessions can be good in the long term due to their potential corrective effects. Recessions can draw attention to long term problems in the economy that have caused problems - things that, if attention is not drawn to them, could potentially cause even deeper problems in the very long term.
I'd argue that a recession is good up to a point. Our housing and related financial markets were unsustainable, and the only alternative was that they were going to get even more absurd over time in an unchecked economy. Also, sometimes people who have newly minted wealth in those economic bubbles often need a reality check to bring them back down to earth and while that's petty, reevaluating one's life when material things go away can often be helpful. Recession often is painful, but the economy and the people usually emerge stronger and wiser.