Main vehicle of Blessing and Curses is words.

Deuteronomy 30:15-20 “See, I set before you today life and prosperity, death and destruction. For I command you today to love the LORD your God, to walk in obedience to him, and to keep his commands, decrees and laws; then you will live and increase, and the LORD your God will bless you in the land you are entering to possess. But if your heart turns away and you are not obedient, and if you are drawn away to bow down to other gods and worship them, I declare to you this day that you will certainly be destroyed. You will not live long in the land you are crossing the Jordan to enter and possess. This day I call the heavens and the earth as witnesses against you that I have set before you life and death, blessings and curses. Now choose life, so that you and your children may live and that you may love the LORD your God, listen to his voice, and hold fast to him. For the LORD is your life, and he will give you many years in the land he swore to give to your fathers, Abraham, Isaac and Jacob.”

Curses come from disobedience. God can not violate a principle or the Word of God.
 
Joshua knew he could take possession of the land after he spied it out. Joshua and Caleb say’s let’s do it. Everyone else reports the negative they see in the land. Moses goes with the majority! And for 40 years--40 years they wander in the wilderness. Joshua knows Moses is taking 40 years of his life, and has to honor Moses anyway. Joshua never dishonored a those is spiritual authority.
 
Joshua went to the promise land and Moses did not. Joshua went on to fight great battles and win.