Don’t go far off, not even for a day, because —
because — I don’t know how to say it: a day is long
and I will be waiting for you, as in an empty station
when the trains are parked off somewhere else, asleep.

Don’t leave me, even for an hour, because
then the little drops of anguish will all run together,
the smoke that roams looking for a home will drift
into me, choking my lost heart.

Oh, may your silhouette never dissolve on the beach;
may your eyelids never flutter into the empty distance.
Don’t leave me for a second, my dearest,

because in that moment you’ll have gone so far
I’ll wander mazily over all the earth, asking,
Will you come back? Will you leave me here, dying?

More information about Neruda from https://www.britannica.com/biography/Pablo-Neruda 

Pablo Neruda, original name Neftalí Ricardo Reyes Basoalto, (born July 12, 1904, Parral, Chile—died September 23, 1973, Santiago), Chilean poet, diplomat, and politician who was awarded the Nobel Prize for Literature in 1971. He was perhaps the most important Latin American poet of the 20th century.

The poem above is a melancholic yet evocative account of separation anxiety which is discussed in clear detail at https://www.counselling-directory.org.uk/counselloradvice10175.html