When we strive to yield to faithful obedience to God.
Many times in life, we find ourselves in circumstances where success seems all but impossible. However, God exhorts His people to be strong and courageous as we carry out His mission. One of the ways in which we can do this is to grow in strength and courage by believing and obeying His Word.
After the death of Moses, Joshua was faced with the task of leading the Israelites. He was faced with leading the vastly outnumbered Israelites against the Canaanites and drive them out of the land. (Numbers 11:28; 33:50-56) As leader of the Israelites he needed particular strength, for if he were weak, the people would certainly be week as well. He needed to know that he could do what the Lord called him to do. Having promised to be with His people (Joshua 1:1-5), God had told him to be strong and courageous. However, they would not succeed if they lived contrary to the will of God. We see this in Joshua 1:7-8, where the Lord promises success only when the people of God meditate on His Word and are careful to obey it.
Although there it isn't one-to-one correlation, there is a connection between blessings and obedience. Sometimes those who obey God's law will suffer and sometimes those who disobey prosper, at least for a time. Those who obey the Lord will win, and those who reject Him will fail for eternity.
When we are obedient to what God tells us to do and so blessed in doing so, we are thereby encouraged to trust in the Lord even more. We must know God's promises in His Word and how He has promised to bless us if we are to grow in the courage and strength He gives to us. "The only way in which we can become truly invincible is by striving to yield a faithful obedience to God." ~John Calvin
"Have I not commanded you? Be strong and courageous. Do not be frightened, and do not be dismayed, for the LORD your God is with you wherever you go" (V9)