How do we know what we’re doing? We see it. How else could we possibly know? It feels like we know things from the inside. We know, perhaps, what we think and feel, but even these perceptions emerge in our awareness, display themselves to us, which also requires a type of seeing. We know something when it makes itself known to us through our various means of perception. Our sensory organs allow this knowledge.
We only see/know, however, after the fact, after an awareness has been presented, which of course must be after the event, emotion or thought occurred. It is, thus, through observation, after the fact, that we know of our actions. Though this claim is highly counterintuitive (and controversial), I don’t see any way around it. We can make countless predictions, based on past experiences of our behavior, which may or may not impart truth of future events, but they guarantee nothing.
Knowing after the fact means we do not know beforehand. I am amazed at how deeply it feels like we can and do know what we are going to do beforehand. Mostly, though, this belief surfaces when we think back on our behavior; it is a product of retrospect. Retrospect, whether a second or year after something has materialized, consists of a notion of prior knowing, which we innately assume to be accurate; we never question it. But, we can clearly see, in any present moment, that we have no sure way of knowing anything we will think, feel, or do next. This element of retrospect is a trick of mind produced by the brain to make us believe we can consciously control our behavior.