There is a difference between a secret and a mystery.

Mysteries have been revealed in the new testament, for example:

Ephesians 6:19 And for me, that utterance may be given unto me, that I may open my mouth boldly, to make known the mystery of the gospel,

Mark 4:11 And he said unto them, Unto you it is given to know the mystery of the kingdom of God: but unto them that are without, all these things are done in parables:

Colossians 2:2 That their hearts might be comforted, being knit together in love, and unto all riches of the full assurance of understanding, to the acknowledgement of the mystery of God, and of the Father, and of Christ;

Although it is revealed in the new testament, it is still hid to them that are not yet saved.

I Corinthians 2:7 But we speak the wisdom of God in a mystery, even the hidden wisdom, which God ordained before the world unto our glory:

It also looks like that a mystery is that which had been secret but was then later revealed:

Romans 16:25 Now to him that is of power to stablish you according to my gospel, and the preaching of Jesus Christ, according to the revelation of the mystery, which was kept secret since the world began,

Psalm 25:14 The secret of the LORD is with them that fear him; and he will shew them his covenant.

btw - it doesn't say he will show us his secret, but his covenant, yet the secret of the LORD is with them

Where? Right there in his word, yet still hidden to them that are lost. 

The LORD has many things secret, and kept secret, but he has revealed to us, in the mysteries in his word, those that he wants for us to know.

Deuteronomy 29:29 The secret things belong unto the LORD our God: but those things which are revealed belong unto us and to our children for ever, that we may do all the words of this law.

Those of us, unto whom he has entrusted his mysteries, do have a responsibility to those mysteries:

I Corinthians 4:1 Let a man so account of us, as of the ministers of Christ, and stewards of the mysteries of God.

Rather than saying to people, "I've got a secret", we should be proclaiming the mysteries, particularly the mystery of the gospel.

Gino