Eternity; what does it mean to you?
Eternity, according to the Merriam Webster dictionary, is the quality or the state of being eternal. And ‘eternal’ refers to an infinite duration. In other words, there is no beginning and no end to eternity. Hence, you do not simply enter eternity from the moment of death. You were there before you die! By deductive reasoning, if there is no beginning to eternity, that should also mean that you are in eternity before your birth.
Eternity can be viewed as an infinitely long time. However, its characteristics do not allow time to be viewed as a sequential and uncontrollable manner. When something is being done in eternity, the process of preparing, doing, and completion last forever. Say, for example, if a song is being sung eternally, then there is no beginning and no end to the song. The song will not have any tune to it for every note will be sung in perfect harmony, eternally.
Eternity then can also be viewed as a place that encompasses all spaces. Being in eternity meant being everywhere. In eternity, there is not a place you can never be; unless you’re being confined outside of it. Hence, you do not simply enter eternity at the moment of death. Rather, you are in a part of eternity as you are reading this.
The basic tenet of eternity is then derived from the idea of a place without a beginning and an end. It is something that we cannot fully fathom while being confined to the earth momentarily, but it will be instantly understood when our consciousness gets us there. 
He has also set eternity in the human heart; yet no one can fathom what God has done from beginning to end. (Ecclesiastes 3:11, NIV)
Understand this and we will understand that what can be seen is temporary and what is unseen is eternal (2 Corinthians 4:18). As God’s chosen people, we are a people holy to the Lord your God, chosen to be His treasured possession out of all people on the face of the earth (Deuteronomy 14:2). This divine ‘choice’ (not the best word to use here in this context) transcends space-time and the created universe. It happened in the realm of eternity that no language can fully express.
God creates and directs the entire human history for His very purpose. This purpose of the entire human history is a mystery that is made known to us through the gospel and through the Holy Spirit – “to bring unity to all things in heaven and on earth under Christ” (Ephesians 1:10, NIV).
The concept of eternity, therefore, encapsulates God’s sovereignty over the elect and the non-elect. God foreplanned freewill on earth and given humankind the ability to do whatever we want. However, those who truly love Him will (according to our free will) keep His commandments (John 14:15).
God did not ‘choose’ people to be with Him in heaven because the act of choosing contains the connotation of a before-and-after decision. Rather, God is already with the ‘elect’ from the beginning since death cannot account for the ‘start of eternity’. The only explanation, therefore, should be this: that we are already with God since the beginning of time, and for the purpose of Christ’s salvation, placed on the earth. Given the freewill during our temporal stay on earth, we have the opportunity to groom and to grow to worship Him with all our hearts, soul, and mind; all of these in preparation for an eternity with Him in which we are already enjoying.
And as for the non-elect, they most probably went out that door from the very beginning with Satan.
God’s purpose for us is an eternity with Him; an eternity that is without beginning and without end. In eternity, the worship of God never ceases (ref Revelations 4). And for the unrighteous, eternal punishment and judgment awaits them (Matthew 25:46).
This illustration attempts to illustrate Eternity.
Eternity is centered upon the eternal sacrifice of Christ on the earth (a small yet significant part of heaven-history), followed by eternal judgment and worship of the Maker. All of these are under the umbrella of the Eternal Presence of God.
In eternity, we will be able to look at all the things that have happened on the earth from the beginning to the end. We will reveal the sacrifice of Jesus as well as all the unrighteous deeds we have done for all of eternity. During then, we will notice that our time on earth – along with the entire human history – is but a small, yet significant part of God’s magnificent plan for us to be where we are. A glimpse of eternity will bring forth worship and thanksgiving. A glimpse of eternity should also give us a blessed assurance of all that is to come.
 – John 14:20 – “On that day, you will realize that I am in my Father, and you are in me, and I am in you.” The term “realize” denotes a moment of ignorance. We do not know until “that day”. The day of the Lord will be a day of complete realization of who God is, and everything that God has foreplanned before the creation of the earth.
Eternal. (n.d.). Retrieved June 18, 2018, from https://www.merriam-webster.com/dictionary/eternal
Eternity. (n.d.). Retrieved June 18, 2018, from https://www.merriam-webster.com/dictionary/eternity