How do you pick work for a group exhibition?- decisions, decisions...

I always find it hard to have to pick a single work for an exhition or a submission. How do you remain objective and step back in order to look at the work without the ''baggage'' of emotions and involment you felt at the time you created it? How do you pick the one piece that is the most representative of your practice or/and the ''best'', whatever that means. What criteria do you use? The advice I was recently given included ''picking the work that represents you the best'' and to ''think about the quality/care in which the work has been put together, ie don't pick the one where the glue is showing..'', that can be a bit of an issue for someone who enjoys drawing/painting on anything and everything and does not in any way produce, or want to produce, prestine work. I am strugglng with picking on piece from the below list (for a painting show). If anyone has time to comment on the one they like best, it would be a great help!!

Work 1

work 2

work 3

work 4

work 5