Always running a surplus is presumably as bad a thing as always running a deficit, but if you can run a surplus On sunny days, then you don't need austerity measures on rainy days
Austerity measures are exactly the wrong strategy for "rainy days", no matter what your debts look like. See how the US bounced back fairly quickly from the 2008 crisis after the stimulus, while countries like the UK are still tightening their belts, because the cuts they've made to date have not had the desired effect.