Many of us are aware that we are bigger than just our physical body. We can sense people standing near us for example even with eyes closed and when we haven't heard them approaching. Or we can sense the emotional state of a person when in their proximity.
The reality is our energy bodies are quite big, they can encompass entire rooms or buildings. So that explains why one person being moody can affect the mood of everyone else. Conversely, when we are feeling very positive and balanced we can help others stabilise their emotions as well. In modern neuroscience this is called resonance. This allows us to be more connected or aware of each other.
However, we are only consciously aware of a small percentage (about 10% I believe is the number) of what drives our decision-making day to day. So in a lot of cases, we are heavily influenced by our environment. If you are an empath and sense people and energies around you very strongly you might also find it overwhelming at times.
The ancient traditions of the mystery schools and shamanic lineages have held the knowledge about the different human energy bodies and how to work with them. They teach us how to stabilise our emotions and influence our environment positively. They also teach us how to lessen negative influence from our environment past or present.