What's the difference between peace and peace?

"Were the sky always without a cloud and the ocean without a ripple the believer would not know so well the God with Whom he has to do; for alas, we know how prone the heart is to mistake the peace of circumstances for the peace of God. When everything is going smoothly and pleasantly—property safe, our business prosperous, our children carrying on agreeably, our residence comfortable, our health excellent—everything in short, just to our mind (liking), how apt we are to mistake the peace which reposes upon circumstances for that peace which flows from the realized presence of Christ. The Lord knows this; and therefore He comes in , one way or another, and stirs up the nest, that is, if we are found nestling in circumstances, instead of in Himself."
CH Mackintosh, Notes on Genesis, 1897

This topic has been on my mind for the past few days. Over the past months I have been extremely agitated, unhappy, and depressed. This has been especially prominent in my relationship with my wife and to some extent with my daughter. However, the last week or so has beecompletelyly the opposite. I have had a certain peace in my mind and life that is independent of the circumstances (except when driving) and thpresencese of this peace has lead to questions. I've been praying for months that I'd be able to get away from this agitated state of mind but it seems it has finally arrived, or has it? I'm not sure if this is just a reaction to fewer stressors in my life or if there has been a really "change". More on this later...