Nothing is accidental. Everything that happens is for a purpose. "Are not two sparrows sold for a penny? And not one of them will fall to the ground apart from your Father," [Matthew 10]. This is not to say, though, that everything is good and beneficial. You have to be accurately discerning about things in your life you should keep or discard. But to be sure, both serve a purpose.
You read a book when you still weren't in Christ or in God's present move. That book wasn't accidental. God purposefully made sure you'd read it and get ideas from it. You took a college course for 5 years and yet later ended up in full time ministry. Nothing in that college course was a waste of time. God intended every moment of it for your maturity in the Kingdom later.
I've read a lot of books--from history to communism and Karl Marx, to romance and drama, to Science and theology. I also loved books on espionage, arts and humanity, human nature and relations, Jose Rizal and other heroes, world affairs, politics, and economy. These weren't just accidental. God gave me interests in them for a purpose.
To be sure, it's not for self aggrandizement or ambition. It's to later humble you and make you wiser for the Kingdom, to become wiser than the enemy [Psalm 119.98]. God has nothing in mind but the Kingdom of his Son. Everything he allows in this world is for Kingdom advancement. So you better align your life priorities accordingly. Everything in your life should be about the King and his Kingdom on earth.
Later, as you grow closer to God and meditate him and his Word more (and as you decrease and Christ increases in you), he starts the winnowing process. It happens in your inner man. He makes you remember a lot of things, especially from books or teachings you heard before and unconsciously stored in your subconscious. We're all, in a sense, like the law teacher Jesus told about in Matthew 13.52.
We keep in our memory storehouse a lot of ideas and concepts (or human theologies) that quietly process our mindset and mold our thinking. Most of them draw us far from God's Kingdom and closer to men's churches, but some of them give us second thoughts about what we're doing.Later, when we join the genuine present move of God and become "disciples of the Kingdom," God moves us to weigh the contents of our minds and hearts and "bring out new treasures as well as old" from our storerooms.
“Therefore every teacher of the law who has become a disciple in the kingdom of heaven is like the owner of a house who brings out of his storeroom new treasures as well as old.”
True Kingdom people become experts about treasures. They know how to use old and new treasures and what among them should be kept or discarded. Old treasures can become new in Christ, and vice versa. Ordinary law teachers who know nothing about God's Kingdom on earth will just keep the old and reject anything new as "dangerous" or "unsound."
"And no one after drinking old wine wants the new, for they say, 'The old is better,'" [Luke 5.39]. No one, except the one who has become a disciple of the Kingdom. Everything is permissible but not all can bring a benefit, says Paul.
As you become familiar with the Kingdom and mature in Christ, you see the true worth of things. You see in the spirit and easily get rid of useless things and retain what has use in the Kingdom.
"But examine everything carefully; hold fast to that which is good; abstain from every form of evil," [1 Thessalonians 5.21]
The whole idea behind is being wiser in God's Kingdom and the purity of the inner man. In Christ, these are among very few things that really matter. The rest is garbage.