Isaiah1:19 If you are willing and obedient, You shall eat the good of the land; NKJV
Kenneth Erwin Hagin told the story about how God dealt with him on an issue during his Pastoral years in the ministry. God told him to leave the church where he was pastoring for another church. He left in obedience to God's instruction but not willingly. He was a bit unhappy about it because the church was taking good care of him and he lacked nothing in that former church.
In the new church, things were hard for him. While praying one day about his needs,he quoted the scripture above to God but God told him that he left his former church in obedience but he was not willing so he couldn't eat the fruit of the land. Some obeyed God truly but in the depth of their heart, they didn't do it willingly. To eat the fruit of the land, you must do the two.
God is a God of principle. Praise God for His unmerited grace but the grace of God doesn't nullify the principles of God. If God gives you an instruction to do a thing, add a dose of willingness to your obedience. When you grumble and obey, you cannot be blessed for obeying, willingness plus obedience releases unto you the good of the land.
Father, I receive the grace to do the two In Jesus name.