The kingdom of God cometh not with observation; neither shall they say, Lo here! or, Lo there! For behold, the kingdom of God is within you.  (Luke 17:20-21)

[T]he kingdom of God is always present for him who desires and wills it. When a man’s disposition and way of life are like that of an angel, most assuredly this is the kingdom of God. For God indeed is said to rule as King when nothing worldly meddles in the governing of our souls and when in every respect we live not of this world. This manner of life we have within us, that is to say, we have it within us when we desire and will it. We do not need to wait a long time, or until our departure from this life; instead, faith and a God-pleasing life which accompanies faith are very near us.  Blessed Theophylact (+c. 1108)

The present age is temporal. In comparison with the future one it is like a drop in the oceans. So no longer attach your mind to temporal and earthly things, but to the incorruptible and heavenly things. Let us long with our whole soul for heavenly things, and with God’s help we shall obtain them. Let your recollections, says Saint Yperechios, be in the Kingdom of Heaven, and you shall quickly inherit it. So please, my brethren, let us not be negligent and drowsy.  Elder Philotheos Zervakos (+ 1980)