Heaven is in both the future and present
As a child, I imagined heaven to be located in the sky because the Bible refers to it as "above". As I matured, I abandoned this belief, but I never questioned why the Bible referred to heaven in this manner. In my perspective both as a child and an adult, heaven seemed to be too far in the future, which was discouraging during difficult times when I needed it to be in the here and now.
I only recently realized that heaven is referred to as "above" because it is located in the spiritual realm, which is a higher realm of existence than the natural realm in which I live. I also recently learned that, despite the fact that heaven is a future destination, God has graciously provided a means for humanity to experience heaven on earth.
Heaven on earth is the Kingdom of God, which is the spiritual domain in which God's (of the Bible) power is manifested on earth. To access this realm, I must be born of both water and spirit. Being born of water is my natural birth, while being born of spirit occurs when I accept the invitation into the Kingdom through Jesus Christ.
Being in the Kingdom not only guarantees my future in heaven, but it also activates my experience of heaven in the present moment. Heaven is my future destiny, and the Kingdom of God is my opportunity to taste and experience heaven in this lifetime.
Clinging to the past and worrying about the future obstructs my experience of heaven on earth; therefore, I will replace my thoughts about the past and future with knowledge of the Kingdom of God so that I may be present to experience heaven on earth.