This is a sad poem, which expresses that even if two people meet, they should not meet again, because it is better not to meet for the first time. This sentence implies that the feelings between two people have changed, or one of them has left, so even meeting will not have a good result.
This sentence can be used to express a sense of loss or nostalgia for the past. It makes us realize that some people and things in life can only exist in memories and never return to the original beauty.