Gratitude is the BIGGEST key to happiness.
Be thankful for what you have but with a desire for more.
Complacency is a mindset killer, that is not what we're preaching here.
Creating a mental make up based in gratitude will create a positive perspective for every situation, knowing that whatever is going on could always be worse. You have your health, you have life, and you still have time left to make a change or learn from a negative experience.
Healthy people want many things, unhealthy people just want to be healthy.
Be thankful for that if you are.