My son didn't wear a sleep sack during the summer months when he was in his sleep sack phase. It's been too warm for the winter sleep sack so last night and for naps today, I didn't put my daughter in her sack. It took her almost an hour to finally fall asleep during both her naps. I wonder if not having a sleep sack has to do with it. I wonder if I need to get her a light sleep sack for the summer.