The Bible tells us the condition of our heart:
The heart is deceitful above all things, and desperately wicked: who can know it?
Having the understanding darkened, being alienated from the life of God through the ignorance that is in them, because of the blindness of their heart:
Take heed, brethren, lest there be in any of you an evil heart of unbelief, in departing from the living God.
The Bible tells us how to have a new heart:
But what saith it? The word is nigh thee, even in thy mouth, and in thy heart: that is, the word of faith, which we preach;
That if thou shalt confess with thy mouth the Lord Jesus, and shalt believe in thine heart that God hath raised him from the dead, thou shalt be saved.
For with the heart man believeth unto righteousness; and with the mouth confession is made unto salvation.