The list that follows is famously unsentimental. A time to be born and a time to die; a time to plant and a time to pluck up; a time to keep silence and a time to speak. The Preacher is not offering comfort so much as accuracy. Life contains all of it, and the seasons are not optional.
What makes the passage bearable is what he says at the end of it: God hath made every thing beautiful in his time. Not everything is beautiful now. Some of these times are plainly not — a time to weep, a time to lose, a time to rend. The claim is that there is a moment at which each will be seen rightly, and that moment is God's to set.
Then a line that explains much of our restlessness: he hath set the world in their heart, yet so that no man can find out the work that God maketh from the beginning to the end. Some translations render it eternity in their heart. We are made to want the whole picture and constructed so we cannot have it. That gap is where most of our anxiety lives.
The Preacher's conclusion is not despair but a kind of freed attention: do good, eat your bread, enjoy your labor. Since you cannot manage the whole timeline, you are released to be present in the part of it you are actually standing in.