Here it seems we are told to be alert. Don’t "faint" (be slack NASB) (7503). But we need to be aware this is another context word. It depends on how it is used and what the circumstances are. Notice in Psalms we are told to relax and let God have His way.
(Psalms 46:10 KJV) Be still, and know that I am God: I will be exalted among the heathen, I will be exalted in the earth.“Be still” is our word “slack.” In Psalms we are told to relax. The NASB says to cease striving.
Our day to day attitude is to be relaxed. God is in control. We can eat ourselves up with anxiety. We can be like me when I watch real wrestling. If I ever watch a match of genuine wrestling I am exhausted at the end. I grunt and groan and twist and strain along with the guys on the mat. At the end I feel like I was in the contest. Sometimes we do that when we should be allowing God to be in charge.
But when a crisis comes we are to move. We are to apply the energy we have saved. We are to bring out the wisdom that has been building up. We become God’s tool of the moment.
So? Is today a day to relax or to push spiritually? That will obviously be different for each of us. Apply yourself whichever way it goes, knowing that God is the ultimate mover of worlds and mountains.