The economy is changing all the time. Today's institutions are quite distinct from those 100 years ago, and will, of course, change in the future, growth or no growth. Any society that has an economy that isn't growing at an accustomed rate will have a lot of unhappy people: irrespective of what its institutions are.
Actually no, you can't make that assumption - because, things are changing all the time. So, it can't always be true, and in fact a society with virtually no growth but a population declining by a considerable amount every year might still have quite fine median income growth and a surfeit of employment opportunities for youth (as elders leave the workforce).
Of course I'm being the devil's advocate there, but to some extent that does describe Japan: it really isn't anywhere near as 'unhappy' as you'd expect a country with no growth for decades to be.