The doctrine of predestination is an important doctrine not as a matter of erudite speculation and empty ponder but as a matter that is deeply comforting to the soul.
Consider John Knox's words:
"The doctrine of God's eternal predestination is so necessary to the church of God, that, without the same, can faith neither be truly taught, neither surely established; man can never be brought to true humility and knowledge of himself; neither yet can he be ravished in admiration of God's eternal goodness, and so moved to praise Him. And therefore we fear not to affirm, that so necessary as it is that true faith be established in our hearts, that we be brought to unfeigned humility, and that we be moved to praise Him for His free graces received; so necessary also the doctrine of God's eternal predestination. (qtd. The Mighty Weakness of John Knox,p.85)
The doctrine is not terrifying but of great comfort and assurance to the Christian. Our understanding of the doctrine comes as we bend our will to what God's Word says. We submit. In understanding the doctrine we are lead to greater worship. We bow lower and exalt God higher in our worship.
John Knox writes:
There is no way more proper to build and establish faith, than when we hear and undoubtedly do believe that our election...consisteth not in ourselves, but in the eternal and immutable good pleasure of God. And that in such firmity that it can not be overthrown, neither by the raging storms of the world, nor by the assaults of Satan; neither yet by the wavering and weakness of our own flesh. Then only is our salvation in assurance, when we find the cause of the same in the bosom and counsel of God. (qtd. The Mighty Weakness of John Knox, p.86)
The doctrine of predestination is a great comfort and assurance. Just as a Christian was elect before the foundations of the world, the Christian also knows that nothing can jar them from the hand of God. They are kept safe from beginning to end the the Lord Jesus Christ who has purchased them and applied salvation to them. Your staying power in the grace of God depends not on you, but on the God who elected you and called you to Himself. He will bring your salvation to completion. Great assurance indeed!