As the expression goes by "When sorrows come, they come not single spies, but in battalions" so are troubles which always seem to come in groups, never just one alone. It means that when sad times come, sorrows, it seems they never come just individually. A lot of troubles seem to come at the same time, not just one at a time. When something sad happens in our life, it usually doesn't come alone - we normally find that lots of sad events come at the same time. (A bit like buses - you wait ages for one and then three come along in quick succession!). When bad things happen, they don’t come one at a time, like enemy spies, but all at once like an army. People are confused since the thought comes about why such incidents have to happen and feel victimized. However, one needs to work on each trouble one at a time rather than handling all at once. Troubles inadvertently are a bunch of sorrows its like they say, bad things come in threes. And I think sorrow comes in many ways. Small disappointments throughout the day and huge blindsiding catastrophes that strike us suddenly. I find comfort, though, that Shakespeare recognized sorrow as it is, named it, and we hundreds of years later can still relate.
Shakespeare's quote simply is observing that sorrows tend to be experienced at the same time as other sorrow, or during a period which, in retrospect, seems to be inclusive of other sorrows. I believe One legitimate sorrowful experience can create a mind-state which precipitates the recognition of other occurrences as being similarly sorrowful. If objectified by the observer, these later occurrences would not likely be identified with in the same way, as evidenced by the usual remembrance of only the first genuinely sorrowful occurrence.
My feeling is that there is nothing in life but refraining from hurting others and comforting those who are sad... as they are feeling left alone and lonely which is tough as it is, but still exist ... As they say that when trouble comes you should close ranks, meaning, to get closer to each other, to help or protect each other, to stand together. Life should be made pleasant ...