You are most probably familiar with the Covey Matrix (or Time Management Matrix). In my opinion this is a powerful tool to be used for all aspects of our lives including complex projects and their management.
Covey initiated this concept in his best seller book « The 7 Habits of Highly Effective People ». The idea behind is to divide your tasks according to 2 parameters : Importance and Urgency.
The challenge is then stay « above the line » (see the below table). In other words to stay mainly in the boxes I and II (Important Tasks whether they urgent or not) and eliminate or drastically reduce activities related to the boxes III and IV (Not Important Tasks).