Answer:
Eustress is not defined by the stress or type, but rather how one perceives that stressors (e.g. a negative threat versus a positive challenge). Eustress refers to a positive response one has to a stressors, which can depend on one's current feelings of control, desirability, location, and timing of the stressor.
The excitement of a roller-coaster ride, a scary movie, or a fun challenge are all examples of eustress. The anticipation of a first date, the first day at a new job, or other exciting firsts also fall under the umbrella of eustress. Eustress is a type of stress that is actually important for us to have in our lives.