The most important ingredient of a long, happy, and successful life is self-discipline.
You also need to develop resilience and tenacity. Without these three things, your life will likely be poor, short, and unhappy. I received them in Marine Corps Boot Camp, Parris Island, in 1964. If you lack the fortitude or foresight to serve in the military, you need to get them someplace else.
Discipline yourself to maintain a normal weight. Obesity is the second largest cause of premature death.
Discipline yourself to get regular exercise. You'll feel better and live longer.
The most valuable thing you can own is a good reputation.