Eccelsiastes 3:1-22 contains an eight-verse poem and theological commentary on the unpredictable reality of earthly existance. There is a time for everything, and therefore nothing stays the same for a very long time.
There are some profound theological, and thereby also practical, lessons for today from this passage.
First some theological lessons. God is the One Who appoints every moment of time, be it the seasons of life, or simply any one moment on the endless ticking of the clock. Therefore, we confidently also affirm that God knows what is next. The unpredictable to us, is the already-predicted to God. But, as this passage affirms, God intentionally does not tell you and me what has been predicted. No believer, much less an unbeliever, is able to know the future, nor even the next change.
Those are all profound theological truths. The resulting relevance to us who believe those truths is that by trusting God, we need not fret about the next possible change to our lives. We can indeed live a seemingly care-free life, while being so fully aware of the worrisome changes characteristic of this life. Without being naive, we can enjoy each moment for the good it holds, and not worry about the inevitable cycles of evil and disaster. We can truly enjoy this earthly life, without having our heart set on it. When evil befalls, we rest in the arms of the sovereign God, and when blessing is received, we enjoy it with great thankfulness.
For everything there is a time, yet, at every time, it is our knowledge of God that fuels our attitudes and responses.