To keep your cookies soft (or to make cookies that are a little too crispy softer) store them in an airtight container with a piece of bread.
The cookies will absorb the moisture from the bread. Change the bread every few days when it drys out.
I did this the other day when I over cooked my cookies by about a min or two. I really like soft cookies, and by the next day they were perfect.
Try it. Promise it will work. Your cookies will be soft and yummy for all of the holiday season.