PUT FIRST THINGS FIRST

To live a more balanced existence, you have to recognise that not doing everything that comes along is okay. There's no need to overextend yourself. All it takes is realising that it's all right to say no when necessary and then focus on your highest priorities. 

Habit 1 says, "You're in charge. You're the creator." Being proactive is about choice. Habit 2 is the first, or mental, creation. Beginning with the End in Mind is about vision. Habit 3 is the second creation, the physical creation. This habit is where Habits 1 and 2 come together. It happens day in and day out, moment-by-moment. It deals with many of the questions addressed in the field of time management. But that's not all it's about. Habit 3 is about life management as well--your purpose, values, roles, and priorities. What are "first things?" First things are those things you, personally, find of most worth. If you put first things first, you are organising and managing time and events according to the personal priorities you established in Habit 2. 

Taken from the seven habits of highly efficient people.

Source: https://www.stephencovey.com/7habits/7habits-habit3.php