In my single, limited case:

A few habits/routines (example - my pre-sleep/bedtime "rituals") are essential for keeping me from crashing, but by themselves they do not create happiness.

I never saw results from my attempts at "positive thinking".

Habit change at my age is next to impossible. Amazingly, I have been able to change or recover habits/routines, but that has not produced change in my mental health status.