When Joshua took over the leadership from Moses, the Lord commanded him to "Be strong and very courageous. Do not be afraid; do not be discouraged, for the Lord your God will be with you wherever you go." What lies ahead beyond the Jordan river, is unknown territory. This will be the first time Israelites will be going beyond their comfort zone which they have wondered for 40 years. The reminder was timely, and God wanted to assure Joshua that He is with him, during this moments of uncertainty and unchartered paths.
There will be seasons in our lives where we are called out of our comfort zone, be it by circumstances or by our choices. More often than not, God doesn't show us the end goal, but wants us to trust completely in Him to lead us through. Many times, we walk in trepedition and fear, because not knowing what lies ahead, is scary stuff. That's why He reminds us. Be STRONG, COURAGEOUS, BRAVE. Have no fear, for He is with us, and we will be victorious, just like how Joshua is.