When someone drains your energy you allow this person to affect your state of being. You can perceive this person as negative, pessimistic, or difficult. The energy drain occurs when you resist the person as he/she is. As a result, you give this person attention either through excessive thought or a behavioral response. Instead, it's better to focus on yourself and to understand that the only person you can change is you. Like this you keep your energy for yourself. Focus on your sense of well-being instead of relating it to someone from your environment.