Someone already mentioned the community aspect, but I’d like to add gratitude.
I think there are studies/evidence to show that consciously cultivating a feeling of gratitude is good for our mental health and happiness. Everyone has some things in life that are good, big or small, and it can be so easy to take everyday things for granted. Taking time each day to think about how lucky we are, and be grateful, is part of many religious people’s prayer practice. Obviously anyone could do this without believing in a god, but we don’t tend to as often without that framework.