We are never promised an easy ride through life. We may be asked to accomplish a seemingly impossible task. Those on the outside will rattle off a "have faith" quip and move on. But here we see God giving Joshua a pep talk.
Joshua had been mentored by Moses for the last number of years, but he was not Moses. He was not the one speaking with God on the mountain. People didn't rebel against him, only to be swallowed by the earth when God Himself defended Moses' position of authority. He was there, but he was not the one in charge. Even the cloud pillar was no longer part of the daily camp life. It must have been a lonely feeling.
"Be strong and of good courage" verse 6
"be thou strong and very courageous" verse 7
"I command thee to be strong and of a good courage" verse 9
Each verse increasing in amplitude, culminating with God commanding Joshua to get ready to be the leader of Israel.
The result? 9 verses later we see Joshua encouraging the tribes to be "strong and of a good courage" verse 18.
Most of us will not be tasked with re-conquering the promised land or leading a nation. But each of us have opportunities each day to encourage a leader or to be a leader who encourages others.
Go out. Be strong. Be courageous.