Firstly, take care because we all fall into the “same” things which were done by others even in the “ages” before.

“There is a thing of which [one] saith: ‘See this, it [is] new!’ already it hath been in the ages that were before us!” (Ecclesiastes 1:10)

Next, make this a point of practice “as much as possible” in order to live peaceably with all men:

Reconcile.

Since we believe in Christ Jesus Who Wills all to be reconciled to Him, so we must in our little lives make steps toward reconciliation with everyone around us.

If our reconciliation is rejected, no worries. We have done our Christ-like duty.

“how that God was in Christ — the world (all) reconciling to Himself, not reckoning to them (all in the world – mentioned prior) their trespasses; and having put in us the word of the reconciliation,” (2 Corinthians 5:19)

Read “literally” with no interpretation from any man and you’ll see the Truth more vividly.

“His Words are Life; not Death”

Now, God’s Secret has something to do with Universal Reconciliation.

Secret of God

The “Secret” “hid” from “ages before” mentioned in

“the secret that hath been hid from the ages and from the generations, but now was manifested to His saints,” (Colossians 1:26)

Which results in “the hope of glory” due to “Christ being in us” and also because “He had made known of it to us” as the verse below also states:

“to whom God did will to make known what [is] the riches of the glory of this secret among the nations — which is Christ in you, the hope of the glory,” (Colossians 1:27)

What is that “Secret”?
The “Reconciliation” of “all things” (Universal Reconciliation in Christ) as the verse prior describes this Ultimate Truth:

“and through Him to reconcile the all things to Himself — having made peace through the blood of His cross — through Him, whether the things upon the earth, whether the things in the heavens.” (Colossians 1:20)

The big picture of the “Secret” is given but the details remain hidden.

Yes, it is sometimes also referred to as the “Secret of His Will”

Secret of His Will

“All” wisdom,

“in which He did abound toward us in all wisdom and prudence,” (Ephesians 1:9)

Centers around knowing the “secret of His Will”,

“Having made known to us the secret of His will, according to His good pleasure, that He purposed in Himself,” (Ephesians 1:9)

That in “fullness” of the “times” (not all in the same time), He “Saves all” (gather in one to save all things in Christ)

“In regard to the dispensation of the fullness of the times, to bring into one all things in Christ, both the things in the heavens, and the things upon the earth — in Him;” (Ephesians 1:10)

Because it’s His Secret Will, again, the big picture (of the Reconciliation of the world = all things) is mentioned literally but the details are not.

Lastly,

That ye may understand

The Secret or Mystery of Christ centers around the “restoration of all things” (Acts 3:21) by the “gathering in one of the all things” (Ephesians 1:10) with the “purpose of the ages” (Ephesians 3:11) meant to “Reconcile all things to Himself” (Colossians 1:20) endorsing the Messiah, Lord Jesus Christ as both the “Saviour of all men” (1 Timothy 4:10) and also as the True “Saviour of the World” (1 John 4:14).

The Mystery (or Secret in Greek) of the Gospel of Jesus Christ regarding our Blessed Lord is revealed thus (in its big picture minus the details which remain hidden till that Day).

That’s a reason why apostle Paul writes that “ye may be able to understand my knowledge in the Mystery of Christ” (Ephesians 3:4) and why such a True “Love passes all knowledge” (Ephesians 3:19):

Ephesians 3 ►

Young’s Literal Translation

1For this cause, I Paul, the prisoner of Christ Jesus for you the nations, 2if, indeed, ye did hear of the dispensation of the grace of God that was given to me in regard to you, 3that by revelation He made known to me the secret, according as I wrote before in few [words] — 4in regard to which ye are able, reading [it], to understand my knowledge in the secret of the Christ, 5which in other generations was not made known to the sons of men, as it was now revealed to His holy apostles and prophets in the Spirit — 6that the nations be fellow-heirs, and of the same body, and partakers of His promise in the Christ, through the good news, 7of which I became a ministrant, according to the gift of the grace of God that was given to me, according to the working of His power; 8to me — the less than the least of all the saints — was given this grace, among the nations to proclaim good news — the untraceable riches of the Christ, 9and to cause all to see what [is] the fellowship of the secret that hath been hid from the ages in God, who the all things did create by Jesus Christ, 10that there might be made known now to the principalities and the authorities in the heavenly [places], through the assembly, the manifold wisdom of God, 11according to a purpose of the ages, which He made in Christ Jesus our Lord, 12in whom we have the freedom and the access in confidence through the faith of him, 13wherefore, I ask [you] not to faint in my tribulations for you, which is your glory.

14For this cause I bow my knees unto the Father of our Lord Jesus Christ, 15of whom the whole family in the heavens and on earth is named, 16that He may give to you, according to the riches of His glory, with might to be strengthened through His Spirit, in regard to the inner man, 17that the Christ may dwell through the faith in your hearts, in love having been rooted and founded, 18that ye may be in strength to comprehend, with all the saints, what [is] the breadth, and length, and depth, and height, 19to know also the love of the Christ that is exceeding the knowledge, that ye may be filled — to all the fulness of God;

20and to Him who is able above all things to do exceeding abundantly what we ask or think, according to the power that is working in us, 21to Him [is] the glory in the assembly in Christ Jesus, to all the generations of the age of the ages. Amen.

P/S:
That’s why the Bible is thick; this unravelling of the Mystery or Secret of Christ to solve all problems caused due to “sin” via the destruction caused by the “god and princes” of this age.

The “non-secret” part is where if we believe in Christ Jesus now, we’ll be saved here itself whilst on earth as a testimony of this truth to the world.

Remember,

“When He (the Spirit of Truth) comes, He will prove the world to be in the wrong about sin and righteousness and judgment:”

about sin, because people do not believe in me;

about righteousness, because I am going to the Father, where you can see me no longer;

and about judgment, because the prince of this world now stands condemned.”
(John 16:8 – 11)