Luke 10:23-24–Then turning to the disciples he said privately, “Blessed are the eyes that see what you see!  24 For I tell you that many prophets and kings desired to see what you see, and did not see it, and to hear what you hear, and did not hear it.”
Whenever we find ourselves discontent with our lives, one way of shifting our attitude is to consider the things that God has enabled us to experience.  Salvation being the most important, and along with that, seeing God work in our lives.  So whenever discontentment rules your soul, consider this, you are experiencing things from God that many people yearned to experience but couldn’t…
Without having a “benchmark” to measure why we should be grateful, we begin to think we deserve and should have everything without measure!  Never considering, that maybe our parents generation would have been overwhelmed with the blessings/experiences that God has showered upon us?  We have to conclude, that it was God’s mercy to show us such blessings and experiences, because He never had to.  The moment we act as if He is supposed to give us what He decided to give, we are acting spoiled! (Matthew 11:21, Luke 11:13)
We can find our hearts not being grateful with what God has privately shown us, because our gratitude isn’t coming from faith in relationship.  Not seeing every “good and perfect gift” coming from the Lord, but rather people or ourselves!  So the moment we become discontent with people, we can lose gratitude for what God has disclosed to us to be grateful for, namely Himself and the blessings of salvation! (James 1:17)
Jesus wanted the disciples to understand, that what they were doing in His power in seeing the Kingdom revealed, was for them to be grateful, and not waste it, or take it for granted.  Because you had people who had come before them, not have that privilege.  Jesus knew they had no experience in themselves to compare it to, but they did have people who came before them who had less, and lived grateful and passionately for God.  The disciples were blessed with even more, and expected to do the same…(Luke 12:48)
Gratitude finds it’s consistency in walking daily with Jesus Christ.  Without gratitude to God for what we have that is “good”, whether in relationships, family, career, etc. we will waste it.  So as incapable as we may see a spouse, or difficult children, job or ministry, the ability to be grateful is to know God has privately revealed His goodness through relationship.  Something everyone doesn’t have the privilege to experience, yet God has disclosed it to us, His children.  Let such a privilege overshadow your discontentment, to prove that He is your Lord.  A grateful heart will cancel out a bitter discontented heart, and vice versa…(John 15:16, Hebrews 12:24-29, James 3:12)