None of us is born knowing the difference between a situation and our experience of a situation.
There's so much Buddhism-inspired hype in contemporary self-help about "being in the moment". I don't know how much of it is completely missing the point.
But there is a point, and it's a good point.
The good point is not "you should spend all or even most of your time attending to immediate sensory experiences, rather than remembering the past, imagining the future, or entertaining abstract thoughts." How dare you pass by a flower without stopping to smell it! Unfortunately, that's the easiest thing to take away from anything that talks about "mindfulness" or "being here now".
When attempting to state the useful insight of "be here now", I find myself tempted to say things like, "Immediate experience is all we have." I don't say it, because I expect it to sound like nonsense to anyone who doesn't already know what I mean by it. I'll try it a slightly different way.
Problem solving tends to benefit from an accurate model of the situation, the available tools, and the problem solver. No matter what you do, every action will be directed by a mind that exists within its own bubble of immediate experience. We actually don't have a very good model of immediate experience by default, despite spending every moment of our lives in it.
When you imagine a future version of yourself, your attention is not on that with which you're immediately acquainted. It's on an attempt to model the future, and attempts to model the future call on memories of the past. Memories of the past are not faithful models of immediate experiences.
Most of immediate experience is forgotten. Most of it doesn't matter, isn't vivid, isn't unusual, doesn't make a lasting impression. It takes an extra reflective effort of become aware that your mind's doing whatever it's doing. A lot of the truth of what it is to be a mind slips through the cracks. So our default models of immediate experience lack crucial information.
Additionally, they equivocate between objects and representations of objects.
From a distance, you don't have separate memories of hearing your partner's voice become strained, seeing their facial muscles tighten, interpreting their words as insults and accusations, feeling a shadow of anger and believing it is the emotion they feel. You don't have a memory of sense impressions and interpretations, of forming hypotheses and weighing evidence. Not unless you've trained that specifically. You just have a memory of your partner being angry.
If you use that memory to plan for the future, at some point you're going to run headlong into the impossibility of experiencing your partner's anger directly. Where does your partner's actual anger exist? In your partner--and thus outside of your experience. That event just isn't available to you.
Why not?
Because immediate experience is all we have.
There, I said it.
It is the capacity to recognize all the features of immediate experience, without intrusion by mnemonic distortion and object-representation equivocation, that is cultivated by a practice of "living in the present moment".
It doesn't always work. Maybe it almost never works. I'd bet, though, that it works sometimes, and that almost nothing else ever does.