Like particles or waves of light, behavior is shaped through 'reasons', those stimuli impinging on us or created by us that as arranged and conceived through conceptual metaphor 'drive' behavior. But behavior passes through a similar aether that seems to shape behavior independently of the objective reasons we have to behave. This psychological aether is called attention. For every moment of existence, we are just swimming in attention, the eddies and currents of awareness that sculpt behavior like water shapes a rock. Whatever we do, however we are doing it, attention is there as the medium through which behavior flows. That is, attention, like aether, allows us to get by. Yet do we need it?
Well, no. Attention is not a thing, but an aspect of a thing. It is no more than a taxonomy or classification scheme for the specific events that drive behavior. Paying attention means nothing in itself, save for the stimulus events rendered as cognition or behavior that 'occupy' and thus define attention. In psychology, attention is rarely used as an independent or controlling variable, yet nothing we see or do can take place without using the term. That is because attention is, like the x factor in 2x=4, a very useful 'unknown' variable, or a descriptor for an obscure event that drives behavior that we will get around to defining, someday. In other words, if we say that such and such behaves in a way because he wasn't paying attention, it ain't attention that's the cause, but implied reasons that comprise attention.
The problem is that attention can become a defacto stimulus, and thus needs no more elaboration, even though it has no stimulus properties whatsoever. To illustrate, in meditation and hypnosis, the causal event of attention is rendered as a specific stimulus event, even though it is never defined. However, if you don't know what your independent variable is, you won't really know what the dependent variable is either. Thus we have psychological magic, with attention being a mere sleight of hand that moves us like a will o the wisp to somewhere we scarcely know. So attention is a great device to define something without defining what you're talking about. (this is also called psychobabble or outright fraud) Indeed, this is a problem we all should pay attention to.