"And I will give you a new heart, and I will put a new spirit in you. I will take out your stony, stubborn heart and give you a tender, responsive heart." (Eze 36:26).
"A new spirit", refers to a new attitude of the mind. Check out the Good news translation.
"I will give you a new heart and a new mind. I will take away your stubborn heart of stone and give you an obedient heart." (Eze 36:26).
When Paul said, "be renewed in the spirit of your mind" (Eph 4:23), he wasn't referring to a spirit being, but an attitude. Sometimes we say this like, "I am doing this in the spirit of Christmas", or "Where is your team spirit", or "School spirit is at an all-time high this period". We are not referring to an actual spirit being, but an attitude.
So when God said, "I will put a new spirit in you", he meant he will give us a new attitude. A new mentality, a new way of thinking and acting. A new character and behavior. A new kind of likes and dislikes, hobbies and things you find repulsive. A new kind of pleasure; you now find pleasurable, things you don't use to find pleasurable. A new and responsive heart is a heart so eagered to do his will. A heart that enjoys God, that is delighted in God. An obedient heart that remain faithful no matter what. This is meant to be the reality of the New Covenant.
"For the law was given through Moses; grace and truth came through Jesus Christ." (John 1:17).
God gave man his standard and man couldn't meet it because we don't have the ability to. Then God decided to make another covenant where he will not just give man his standard again, but he would give us the ability to meet that standard. This ability is called grace. It is the ability to graciously fulfill all of God's requirements and meet his standards effortlessly. God is able to achieve this plan of his by giving us a new heart and a new spirit. This means the new covenant people naturally have a faithful spirit, and they do not have problems with obeying God. Look at us today and how rebellious we have become. Did God lie about the New Covenant? Did he fail to do what he promised to do?
"Certainly not! Indeed, let God be true but every man a liar." (Rom 3:4).
It is us that have failed. Yes, we fail to enter into the reality of the New Covenant that he design. Here we are with our endless debates and contradicting doctrines. We've failed to focus on what really matters. We are meant to focus on Christ, focusing on how to enter into a living experience of the reality in Christ. It's sad that most of us don't even know the reality in Christ, much less how to enter into an experience of it. Rather than to discover the reality in Christ we have been focusing on rules, regulations, rituals and the traditions of man disguised as Bible teaching.
In Christ we have been given a new heart. With this heart we find it very easy to obey God, and we find it very difficult — in fact, impossible — to not yield to God. We have been given a heart and spirit that enjoys yielding to God and fulfilling all his desires. If we are truly practicing the New Covenant then we would experience this reality. I repeat, there is no way you can be practicing the New Covenant accurately and yet not experience this reality. It is either you are lying or God is a liar, and it is impossible that could ever be the liar.
"So God has given both his promise and his oath. These two things are unchangeable because it is impossible for God to lie" (Heb 6:18).
The question you should be bothered with is, "what is the accurate way of practicing the New Covenant so that you can experience this reality?"