All inspirations generally originate from two sources. One is sudden flashes from the internal mind based on past events and experiences and second from the external world, one is witnessing at the moment.
The first source is more often responsible for deep thoughts which force themselves out as creative or destructive expressions in a human being. This is what can be called as an urge to express.
Any observation is valid when done in the present, because only present is the truth or that which is existing for the moment. Past observations only helps to know what was but what is, is known only from the present. The future is invalid for the present since it is absent at the moment.