Happiness lies in contentment and activity

Ishavasyopnishad (ईशावास्‍योपनिषद) says-

“God    is    the    owner   of    all     wealth
that     one   can    find     in     the    world.
Nurture       thyself       as        a     trustee,
wealth      never     remains     with    one.
Be   active   and    while    being    active,
yearn     to     live    for    hundred   years.
Work   dutifully   yet    be   attached   not,
for  thee  this is the  path and none else.”