Deuteronomy 22, Psalm 110-111, Isaiah 49, Revelation 19

Psalm 110:1
In Matthew 22, those opposed to Jesus take their best shot at getting Him to say something with which they could destroy Him.  The Pharisees, Herodians, and Sadducees all asked questions they felt sure would expose Jesus as a fraud.  After fending off all comers, Jesus poses a question to them, "What do you think about the Christ?  Whose son is he?"  They responded "The son of David."  (Matthew 22:41-42)
They had to have thought there is no other answer.  In 2 Samuel 7:11-16, God promised to establish a kingdom for David's son that would endure forever.  Isaiah 9:7 describes the Messiah's kingdom as the throne of David which will last forever. 
Jesus' response completely stumped them.   Referring to Psalm 110, Jesus asked, "How is it then that David, in the Spirit, calls him Lord, saying, 'The Lord said to my Lord, Sit at my right hand, until I put your enemies under your feet?''  "If then David calls him Lord, how is he his son?"  Needless to say, they had no answer, and after that, they questioned Him no further.
Since the Messiah was to be David's son, why would David refer to him as "my Lord"?  We would translate that first phrase, in Psalm 110:1, as "YHWH says to my Adoni."  The questioners could not wrap their mind around the idea that the son was greater than the father.  They could not conceive of David's son also being the Son of God.
I, too, struggle with the thought of God coming and living as a man with all the difficulty and persecution we know Jesus faced.  Why would He lower Himself to such a place?  I know God's love is described in John 3:16.   But why would Jesus do what He did?  John 15:13 provides an answer as Jesus says, "Greater love has no one than this, that someone lay down his life for his friends." 
Jesus, I do not comprehend Your love.  Why would You do such a thing?  Thank You for Your love and obedience to the Father.  Thank You for considering me a friend. 
Isaiah 49:1-6
Isaiah 49:1-6 is a Messianic passage speaking of the true Servant.  In verse four, the Servant says "I have labored in vain, I have spent my strength for nothing and vanity; yet surely my cause is with the LORD, and my reward is with my God." 
I don't understand all that this passage means but at some level in Jesus' humanity; he had to have thought and felt this.  He is the One who said, "O faithless and twisted generation, how long am I to be with you?  How long am I to bear with your?" Matthew 17:17.  "O you of little faith, why did you doubt?" Matthew 14:31. 
This passage has been an encouragement to me because I have felt the same way.  At times, it appeared I spent my time and energy as a pastor for nothing.  But I trusted my cause to the LORD knowing if I am to receive any reward, it is with my God and ultimately belongs to Him anyway. 
In Philippians 2:14-16 Paul explains his evidence of not running in vain.  "Do all things without grumbling or disputing, that you may be blameless and innocent, children of God without blemish in the midst of a crooked and twisted generation, among whom you shine as lights in the world, holding fast to the word of life, so that in the day of Christ I may be proud that I did not run in vain or labor in vain."  Paul's proof of having run successfully are those who through his preaching/teaching hold fast to the "word of life."
LORD Jesus, Your faithfulness is always an encouragement.  I have not faced anything compared to what You endured.  Please forgive me for those periods of feeling like a failure as Your servant.  Thank You for the gift of those who hold fast to Your word because of Your Spirit using me as in instrument in Your hand.