Yes, it is good to think often about your eternity and for me, I when I think of my eternity, I remember this, from the book "So High the Price":
Consider my son, that if you go to hell, you will never leave it. There, every pain is suffered and suffered forever.
Even when a hundred years have gone by since you went to hell, or a thousand, hell will be just beginning.
After a hundred thousand, a hundred million years, after millions of centuries, hell will still be just beginning.
If an angel were to bring news to the damned that God had decided to free them from hell when as many million centuries had passed as there are drops of water in the ocean, leaves on the trees and grains of sand on the earth - if the damned were to hear that, they would be immensely consoled. "True", they would say, "many centuries must yet pass, but some day the time of our freedom will come." In reality, however, such vast stretches of time and more than we can possibly imagine, shall pass and find hell still only beginning.
Every soul damned in hell would be willing to make this agreement with God: "Lord, increase my suffering as much as You will; make me stay here in this place of torment as long as You will, but give me hope that someday You will free me."
But no, this hope, this end to suffering, shall never be.
At least if the poor soul of the damned could deceive himself and cheer himself up by thinking, "Who knows? Perhaps some day God will have pity on me and lift me out of this burning inferno."
No, not even that way is open to him, for he will forever see written before him the sentence of his wretched eternity.
"So", he will say, "all this terrible pain, this fire, will never end for me?"
"No," will come the answer. "No, never."
"Will they last forever?"
"Forever - for all eternity."
Oh, eternity! O bottomless pit! O sea without a shore! O endless tunnel! Who does not tremble at the thought of you!
Accursed sin! What tremendous agony you prepare for those who commit you!