The proverbs put it this way. "Above all else, guard your heart, for everything you do flows from it." The King James Version translates it this way with all diligence, guard your heart. Here it shows the emphasis on the duty we have to guard our hearts with all we have. 

The heart is: 

1. An important place that needs to be protected 
2. A place that calls for deliberate action to ensure its safety
3. A place requires consistency in the duty of guarding

The heart is an important place and the verse highlights it by calling to action "above all else". Above everything we do and where we dispense our energies. We must first give priority to the safekeeping of our hearts. This emphasis places accent on the deliberate actions we must take to ensure its safekeeping and protection. Nothing else must get in the way of our efforts to keep away the things that are intended to corrupt or contaminate our hearts. By all means necessary, we must ensure we are to be consistent in our efforts.  Because the things that are there to infiltrate our hearts is always at work to do so.