As I have said before, we define ourselves by the range and success of our wills. It becomes a problem of folly and then evil when we claim a range and/or a success where we have it not. This is the problem declared by St. James in perfectly reasonable and often echoed plans stated in his fourth chapter, verse 13. "Today or tomorrow we will go into such and such a town and spend a year there and trade and get gain." This is "boasting arrogance". The remedy is not to always live spontaneously but to dodge the arrogance. "If the Lord wills" is the addendum but not for incantational benefit and as a verbal pretend awash in "Christian speak". We state it out of the abundance of our hearts. Our will in our plans is not the highest will. We are but a vapor. Even your continued living will be at the permission of powers higher than thine.
We all enjoy growing our little emotional, financial, or real estate fiefdoms but the evil (which beset many satraps of the Persian Empire) is to be confused by your downline successes. With the focus of your manifest will expected to be a guide and authority for your citizens, you too ought look up at your own overlords with similar clarity. You are a citizen of God's kingdom. He might have other plans. The rich man in Luke 12 was making very reasonable plans. His view was all downward as he said "I will do this... I will store...I will say to my soul.." God said to him, "Fool! This night your soul is required of you." The richness of our selves, found in the expanse of our kingdoms, must be second to the richness of God's kingdom. His rules ours.