As I yawn and consider this, I hear:  "Not by might, nor by power, but by Spirit."  [Zech 4:6]  
Isaiah 40 instructs us:  "He gives strength to the weary and increases the power of the weak...(verse 29) But those who wait on the Lord shall renew their strength; they shall mount up with wings like eagles, they shall run and not be weary, they shall walk and not faint "(verse 31).
Jesus taught us:  "The spirit is willing, but the body is weak."  [Matt 26:41 and Mk 14:38]
Do you recall the old children's song:  "We are weak, but He is strong"?  Did you know that was Scripture?  [I Corinthians 4:10]
The letter to the Corinthians goes on to say, "That is why, for Christ's sake, I delight in weakness...for when I am weak, then I am strong."   (II Corinthians 12:10)
It goes back to abiding and letting Him live through us - as we align ourselves with Him.