It takes time to develop new habits and eliminate old ones. You may have committed to working out, eating right, reading your Bible every day, spending more time in prayer, whatever the changes you want to make are, they will not be easy. The writer of Hebrews told us so Chapter 12 verse 11 says...
"No discipline is enjoyable while it is happening—it's painful! But afterward, there will be a peaceful harvest of right living for those who are trained in this way."
The Greek word the writer uses for discipline is the idea of transforming an undisciplined child into one that is disciplined in all areas. The word used for discipline while certainly has to do with spiritual discipline is not limited to just spiritual it can refer to financial, physical, mental and all forms of discipline. The writer is saying "at this moment in time" it is not enjoyable to be transformed from where I am to where I need to be, in fact, it is a tough task, it causes me agony (painful in the Greek).
The writer is saying, "anytime I need to begin to change to become more of who God wants me to be and bring my flesh under subjection to Christ, it will cause me agony". It is not easy to change, but if you are willing, the promise is, you become more Christ-like, more the destiny that has been planned for you, and you feel more like who you were meant to be. This will bring you into a real place of peace and contentment in all things.
Sometimes when God is calling us to change, it might not seem very spiritual but is necessary to our becoming all the Lord has ordained for us to be. Perhaps the resolution or revolution you have underway in your life is bigger than losing weight, learning something new, eating right, getting into the Word and prayer. It has a broader role to play in God's big picture for you. Deal with the pain of change, knowing your destiny is coming!