It seems to be something of a truth in our lives that we only appreciate what we have and can see the advantages when we don't have it any more or at least are on the point of leaving it. This quote exemplifies this truth, as it helps explore the massive internal conflict that Eveline is experiencing as the point has come for her to leave her home and the many ties that bind her to Ireland. If you have a look at this quote in context (always an important thing to do), you can see that it comes after a list of the negatives about her life:
She had hard work to keep the house together and to see that the two young children who had been left to her charge went to school regularly and got their meals regularly.
Prior to this we are told about how she argues with her father over money and he is something of a despot in the household, only giving her the money she needs for the housekeeping late in the day so that she has to rush out after work to do the shopping that she needs. And yet, as she is on the point of leaving all of this, she finds joy in it and it becomes not "wholly undesirable." The quote therefore relates to the conflict that Eveline experiences and her desire to stay in her life, in spite of her many frustrations.