Is Psychological Wellbeing good for mood & stress?

Yes — the evidence for this is strong. Two independent meta-analyses link dispositional optimism to lower cardiovascular events and all-cause mortality, and a broader synthesis found psychological well-being predicts all-cause mortality independently of the absence of distress — suggesting wellbeing is not just the inverse of mental illness. That's reflected in an evidence score of 72/100 for its role in mood & stress, drawn from 9 studies, with an estimated impact on longevity rated moderate (48/100).