Rescuing the flowers whose stems had gone all mouldy and yuk, I simply snipped them down and put them in my little jug. (I'm sure that 'plant food' they give you at the florist slowly kills your flowers instead of actually feeding them, just so you'll go back and buy some more.)
I had used up all my pot of Parsley and left the little plant pot outside ready to take to the compost bin, obviously I kept forgetting it, well you do don't you, so it was still there a week later and guess what .... it's started growing again. So I rescued it, and now it's in recovery and I'll have a free pot of Parsley.
Next time you use up a pot of herbs, wait and see if yours come back to life.