One thing I would add—Writing a gratitude journal once a week has been shown to be more effective than doing it daily (Sonja Lyubomirsky 2007)
I found two publications by Lyubomirsky in 2007. Only one contained something remotely similar to your claim:
Tkach (2005) demonstrated that participants
who were randomly assigned to vary the types of kind acts they would
perform on a weekly basis showed higher levels of happiness and well-
being 10 weeks later relative to those who did not vary their kind acts,
and relative to comparison controls.
However, this is about “kind acts”, not about a “happyness journal”.
I found two publications by Lyubomirsky in 2007. Only one contained something remotely similar to your claim:
However, this is about “kind acts”, not about a “happyness journal”.
Can you clarify the daily-weekly claim?