Consequentialism tells us that the correct answer to the question what to do is simply whatever's best. Critics object that attempts to calculate what's best often turn out badly. This is often taken to imply that consequentialism is self-effacing: it tells us to ignore its guidance, and forget that it is true. But this is too quick. While it's always an empirical possibility that it'd be most rational to induce irrationality in ourselves, it's less clear that our ordinary non-calculative dispositions are examples of this. That is, I would question whether they must be thought of as manifestations of irrationality (anti-consequentialism).
The crucial point here was developed in my recent discussion of 'Satisficing and Salience', with the distinction between how to answer a question vs. whether to ask it in the first place. To illustrate, begin with a moral datum: it's regrettable that the Great Pyramids were built with slave labour. A rational agent must be responsive to these reasons for regret. But that is not to say that she must always be actively responding to these reasons, for that might distract her from more pressing tasks. So the rational agent need not actively regret everything that is regrettable. Granted, she must be disposed to answer the question correctly when it is raised, so to speak. (She'll feel regret if she attends to this aspect of history.) But it's just a mistake to think that rational agents must constantly be raising the question. Most of the time we needn't think about the regrettable aspects of ancient history at all.
I now propose that we may find something similar with regard to the question how to act. Most of the time we act without conscious deliberation (let alone calculation). That doesn't make us implicit anti-consequentialists, any more than our everyday inattention to Ancient Egyptian slavery makes us implicit slavery apologists. You can't be accused of answering a question incorrectly when the question never arose in the first place. (This is a bit quick: we may also be interested in what sorts of considerations in your immediate environment you're disposed to respond to, for purposes of character evaluation. Someone disposed to neglect or downplay others' suffering - even when it's right before their eyes - could hardly be considered a utilitarian in their heart of hearts.)
Anyway, just as it would be a rational defect of sorts to counter-productively obsess over ancient slavery, so it would be defective to be constantly questioning yourself about what you ought to be doing right now, and now, and now, and now... A significant degree of default trust in your ordinary functioning is required if you are to have any hope of competently acting in the world at all.
So, nobody should think that constant deliberation about what to do is necessary for (or even compatible with) being a well-functioning rational agent. The excessively deliberate agent is defective. This fact about when (not) to deliberate holds independently of our substantive views about how it's rational to deliberate when deliberation is called for. So the mere fact that we shouldn't constantly be calculatively deliberating is not in itself any kind of argument against maximizing consequentialism.
Of course, we can develop a more promising argument out of this. There's no denying that sometimes deliberation about what to do is called for. So we can ask what sort of deliberation would (on those occasions) be rational according to consequentialism -- and then assess whether that answer is plausible. But that's a task for another post. For now, I simply want to establish that we shouldn't understand the consequentialist agent as always having "one thought too many". In most cases, they -- like anyone -- won't think at all before acting.