What are some practical ways to hold onto those brief moments of happiness when life feels overwhelmingly sad?

Why do highly successful people prioritize things like getting 8 hours of sleep and avoiding processed foods?
Was everyone mentally ill in the 70s? Why did architects and home design involve heavy use of ugly tans, browns, yellow, and greens?
What does it mean to be an eternal optimist, and how does it affect your outlook on life, especially during tough times?