Answer:
A poem by its very nature can be continually changed, added to, rewritten; at some stage the poet has to decide that he or she has refined the poem to a point at which they are content to leave it. To get to the stage where a poem is offered for reading, the poet may have working on it for months. At some stage they have to decide to stop reworking, and to consider the poem finished. This is the abandonment that Paul Valery speaks of.