In conclusion, be strong in the Lord [be empowered through your union with Him]; draw your strength from Him [that strength which His boundless might provides].
In the Lord is where a believer can find all the strength they need. Strength to face and overcome any challenge in life. It didn’t say be strong in yourself, but in the Lord. We draw strength from Him when we draw near to Him. All who wait upon the Lord shall renew their strength. Greater is He who is in you than he who is in the world. When we take time to quit our minds, become aware of His presence within us, the very same presence and power that raised Jesus from the dead, we will become aware of His strength. So take time to wait upon the Lord and He will renew your strength and you will mount up with wings like eagles, you will run and not be weary, you will walk and not faint.