The difference between these two strips fascinates me. I think we all know what it feels like to completely lose ourselves in absorbing work or play, to the point where time has no meaning and the need to eat, drink, and pee starts to seem like the greatest possible nuisance. (This is where the Skittles-and-Diet-Coke dinner comes in.) But what makes the difference between emerging from a three-day haze after a marathon writing or coding or animated-film-making session vs. cutting damp rainbow candy out of your hair after losing a whole weekend to Super Mario Brothers? The psychological concept of “flow,” which purports to explain these periods of intense mental absorption, doesn’t capture the distinction between Good and Evil flow, between a warm happy feeling plus a completed article on Jane Eyre and a horrifying 7,674-item browser history.
Here is where it would make sense for me to talk more about the theory of “flow.” Since I know that one of my chief tools of procrastination is internet research — I spent nearly two hours tracking down, downloading, and scanning those two Doonesbury strips — I’m going to just go ahead and paste part of the Wikipedia entry on flow rather than presenting a scholarly portfolio of peer-reviewed citations it would take me three days to compile: “In his seminal work, Flow: The Psychology of Optimal Experience, [Mihaly] Csíkszentmihályi outlines his theory that people are happiest when they are in a state of flow — a state of concentration or complete absorption … a state in which people are so involved in an activity that nothing else seems to matter…. The flow state is an optimal state of intrinsic motivation, where the person is fully immersed in what he is doing. This is a feeling everyone has at times, characterized by a feeling of great absorption, engagement, fulfillment, and skill — and during which temporal concerns (time, food, ego-self, etc.) are typically ignored.* *Csikszentmihalyi, M. Flow: The Psychology of Optimal Experience. New York: Harper and Row, 1990.” 
See: nothing about Evil flow. In my experience, Evil flow is equally characterized by a “feeling of great absorption [and] engagement” in which temporal concerns are ignored. But it is also characterized, later, by sickening regret, a feeling of lost time, intense shame, and intransigent mortality. Let me hasten to clarify: I don’t think that the difference between Evil flow and Good flow is about whether one is left with a product or merely be-Skittled hair at the end of the session. It is entirely possible to feel a warm happy glow after a day of something “non-productive” like playing tennis or reading a novel or baking a cake, just as it’s possible to feel the clammy hands of death at one’s throat after producing 3,000 words of lucid prose.
While it is true that the two categories often track onto one another — Good = Stuff; Evil = Waste — those equivalences are both the manifestation of superego and an epiphenomenon of capitalism. What interests me more is the phenomenological difference: surely something must be going on during Evil flow other than internalized self-loathing. I contend that the actual experience is different, not just the affective outcome. “Evil flow” isn’t enjoyable; it’s compulsive. One of its distinctions is self-recrimination, but I honestly think that has more to do with a sense of non-enjoyment than with non-“productivity.” It is sadistic, and emanates from the realm of the death drive rather than the realm of the pleasure principle — and as such, it is also characterized by self-destructive repetition. We are so often at odds with our own best interests.
My beloved life partner suggests that the distinction is one of value: we feel good after spending time on things we value and not so much when we don’t. I agree completely, but this leaves two central questions unanswered: why does “flow,” broadly conceived, even happen when we are doing things we do not value? Why do we lose track of time and our caloric intake when we’re absorbed in an empty, unrewarding activity just as much as when we’re in an “optimal state of intrinsic motivation”? But more importantly, what determines what we value to begin with? Perhaps flow, in both its “good” and “evil” forms, holds the key to answering this second question; maybe we should track the flow in order to find out what we value, instead of the other way around. “Our desires cut across one another, and in this confused existence it is rare for happiness to coincide with the desire that clamoured for it.” 
As with so many things, only psychoanalysis and literature really speak about this distinction. And, of course, Doonesbury.
 http://en.wikipedia.org/wiki/Mihaly_Csikszentmihalyi. (God, the writing on Wikipedia is abysmal. I elided the most egregious repetitions, but even so. Normally I advise students to stay away from the thesaurus, but I would prefer a misused “stipulation,” “contingency,” or “sovereignty” in place of one or two of those “state”s.)
 Marcel Proust, Within a Budding Grove.