3 Habits - This is a great read for the simplicity and clarity it brings.
These habits as described in the article ring true and are often viewed in other ways and said differently. Here is my outlook.
Contentment
For instance, stoic philosophy probably matches the the idea of contentment rather than looking for happiness at every turn. If you can learn to find peace with what you have and what life has to offer without constantly striving you may find contentment. Of course stoic philosophy is more encompassing in that you gain the means to cope with life's disappointments and challenges. Here is a book that covers the modern take on worry.
Daily Exercise
This is a given no matter what you do with the rest of your life. Lack of movement and physical workout will bring you down. Tennis is my answer to this. Even something as simple as going out and hitting serves is better than finding a spot on the sofa in front of the TV. Find your source of physical activity and make it a habit that you can't break.
Sleep and Rest - Read the article