Deflation means you can buy the same amount of goods (sustaining the same sized economy) with less money. That less money means you have more surplus money to

Deflation means you can buy the same amount of goods (sustaining the same sized economy) with less money. That less money means you have more surplus money to spend on luxuries. More people will have more disposable income, which likely would mean they buy more goods, and could sustain a larger economy... leading to economic growth. Plus-- the goods you're buying are made by companies who are buying materials at a lower cost, and thus if they lower prices slower than the materials prices are going down due to inflation they have more margin. Businesses as well will have more flexibility, the ones that are borderline now will last longer, might turn things around, etc.