Performance is best for most tasks when you are experiencing levels of arousal

Performance is best for most tasks when you are experiencing high levels of arousal. A person’s level of arousal can be defined as a purpose of attentiveness, situational consciousness, watchfulness, level of disruption, stress and way of attention. In result of how prepared a person is to do suitable responsibilities in a well-timed, prepared and effective method. There are some factors that ease a person to achieve at a best level are flexible and unusual to the individual. Definite elements are often communal such as amount of work, task complication and difficulty, task understanding and past experience, circadian rhythm, degree of related risk if failure happens, own and crew motivation, working surroundings, level of individual stress, health and relational relationship. 

Where is the graph i don't see the graph