I think heaven is the state we find ourselves in once we repent of our sin. Peace of mind. Contentment.
It's only after we are renewed by the Spirit of God that we become joint heirs with Christ. It's at that time we receive the indwelling of the Holy Spirit that we know the Kingdom of Heaven is at hand, but yet not here on this present Earth until the time Christ comes for His Bride and then establishes his Kingdom here on Earth after the New Heaven and New Jerusalem are ushered down as is even being prepared for us in Heaven right now.
John 3:3 Jesus answered and said unto him, Verily, verily, I say unto thee, Except a man be born again, he cannot see the kingdom of God.
John 3:4 Nicodemus saith unto him, How can a man be born when he is old? can he enter the second time into his mother's womb, and be born?
John 3:5 Jesus answered, Verily, verily, I say unto thee, Except a man be born of water and of the Spirit, he cannot enter into the kingdom of God.
John 3:6 That which is born of the flesh is flesh; and that which is born of the Spirit is spirit.
Romans 8:17 And if children, then heirs; heirs of God, and joint-heirs with Christ; if so be that we suffer with him, that we may be also glorified together.
Rom 10:9 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.
Rom 10:10 For with the heart man believeth unto righteousness; and with the mouth confession is made unto salvation.