I think something like 'In three words I can sum up everything I've learned about life: it goes on.' by Robert Frost can work well. It gives a sense of the ongoing nature of life and could fit into various storylines.
Well, a famous quote like 'The only way to do great work is to love what you do.' by Steve Jobs could add depth to a short story.
A quote like 'Not all those who wander are lost.' by J.R.R. Tolkien could be a good choice. It can imply a character's journey or their search for meaning in a short story.