It is really important that you structure your groups in such a way that there is ample time for closure work. It is easy to get carried away by the enthusiasm of group members or to forget the time and then people will leave the group in a stimulated or even anxious or hyperactive state. We all need to cool down after any type of mental or physical activity and have a period of calm. It does not need to be deep relaxation as that could put people to sleep but it does need to enable people to leave the group calmly and as individuals. This especially applies if they have been doing intense groupwork together.