It hurts to spend time growing seedlings and then do something stupid. I had a nice crop of Roma tomatoes growing and have been putting them out during the day to harden off and get more light, then bringing them in at night. One night I forgot to bring them in, and yep, inevitably, that was the night we had frost. Five survived the cold. They look a little sad. Of course it is going to set their growth back. Still, five surviving is better than none.