In games like Fallout or Mass Effect you often have dialog options. These happen during conversations where you can choose between three or four things for your character to say. Now at first you might complain that this system is very limiting, you can only choose what you say out of the options the game presents you with. You lack the freedom of real life where you can choose to say or do anything at all.
I propose that in real life our options are also limited. In the middle of a conversation you can really only choose to say something that you can think of. In the moments between the other person asking you a question and you responding you can’t think of every possible thing you could say. Only one or two or maybe a few ideas will pop into your head. Then you choose the best one, say it, and see how they resond. Then hours later you’ll think of something better, you’ll think of the thing you “should” have said. But basically you couldn’t have said that, it was impossible to say it, because you didn’t think of it at the time. And you can’t possibly say something that doesn’t occur to you.
The same thing happens with our actions. Often we have more time to make big decisions and that extra time lets us think of more choices to consider but we still can’t think of every single possible action. When I’m trying to decide where to eat lunch I sometimes find myself in the middle of the meal when I suddenly think of another place that I would have preferred. But I didn’t even think of that restaurant while I was making the decision. Technically I could eat lunch at any restaurant in the city but realistically that’s too many choices to think about. So I chose from the dozen or so that I thought of at the time.