Activity Cycle
A sense of cycle and recurrence is prevalent in Reality. Practically anything that happens can be understood as having a beginning and an end. You may be familiar with the idea of "the Hero's Journey" from the world of story-telling. There is a level of correspondence between the logic behind the Hero's Journey and the activity cycle as presented and described here.
A Basic Cycle of Activity
In the basic activity cycle there are three time segments to consider: 1) The time before the activity begins, 2) the time during which the activity unfolds, and 3) the time that begins once the activity ceases. The transitions between the time segments are also of interest. The first transition goes from rest to activity and is characterized by the introduction of a motive force — a 'call' to engage in the activity. The second transition goes from activity back to rest and is characterized by the depletion of the motive force.
In the above description, you should understand rest not necessarily as total rest, but rather as a relative peace, a state of affairs that could be described as "business as usual".
A Call-to-Action
You can assume that the transition from rest into activity is driven by some force. This force is felt as a 'call to action' by the agent (the "hero"). This call comes as a change in the context, which becomes a tension that motivates the agent to engage into activity. The idea of a call-to-action also involves a sense of affordance.