People come in all shapes and sizes and varying degrees of complexity. However, it helps to understand and be aware of some of the below energy sucking folks.
Angry People. Anger is a chemical reaction and is perpetuated by the fight or flight response. This anger is intense and it tends to go away quickly. Yet it leave consequences, like broken relationships in it's path. Some people wear anger like a T-Shirt or an Armour to protect them. In other words, they may flare up but more likely they wear the anger around with them in a cold stare or easy dismissive behavior of others. This regular anger can take a long time to recognize the pattern as it is controlled and diliberate.
Insecure People. These people may seem fragile, take things personally and can be easily hurt. You may find yourself being cautious and deliberate with them so as not to upset them. Many people can cast pity or feel sorry for these souls however understand they are getting some kind of reward for their meekness. For instance, your cautiousness may exclude them from heated discussions or tough projects. There is an overall cost to the workplace in lost productivity as people tip toe around trying them to avoid discomfort.
Apathetic People. These people often give off the attitude that they just don't care. They seem reluctant, uncommitted, unwilling, uninvolved or disinterested. These people need to spark a sense of curiosity and wonder about the work they do. They need a renewed sense of purpose and meaning in their work.
Patronizing People. Some people have a way of belittling others and making them feel unimportant. They operate through a smoke screen of importance, talking themselves up and putting others down. Patronizing people either really feel superior to others or they need to act like they are to cover up their insecurities.
As much as people may will it to be, overall the workplace is not a harmonious, pleasant place. It is work, not a vacation, Peoples belief that a workplace should be congruent, happy, and desirable is unrealistic and can weigh down on morale.
Naturally conflict can come to the surface at work because people are constantly under pressure to work to their best and they often don't have the time, resources or control over their results.