I am continuing with my interpretation of the book. Everything in italic is a direct quote from the book.
16. Hence the saying: The enlightened ruler lays his plans well ahead; the good general cultivates his resources. 17. Move not unless you see an advantage; use not your troops unless there is something to be gained; fight not unless the position is critical. 18. No ruler should put troops into the field merely to gratify his own spleen; no general should fight a battle simply out of pique. 19. If it is to your advantage, make a forward move; if not, stay where you are. 20. Anger may in time change to gladness; vexation may be succeeded by content. 21. But a kingdom that has once been destroyed can never come again into being; nor can the dead ever be brought back to life. 22. Hence the enlightened ruler is heedful, and the good general full of caution. This is the way to keep a country at peace and an army intact.
A clear-headed leader plans well ahead and gathers resources. Do not move unless there is a strong advantage to be gained. Do not put your team into danger unless there is something significant they can bring back from the confrontation. Do not enter into a confrontation unless the position you are gaining or defending is critical to the plan. Never put your teams or allies in a difficult situation because of personal pride or grievances. Ask yourself whether there is an advantage to the forward