I often feel the other way round.
I know exactly what I need and want, but I can't get it because it's out of stock or no longer made. Since I'm very picky with material things and don't take the first thing I see, I often walk out of a shop without buying anything (although I haven't been shopping for months).
But when I'm wandering rather aimlessly through the aisles, sometimes something falls into my hand that I could well use or that I've been looking for for a while and had just forgotten about. Or I discover something that fits someone else and I seize the opportunity.
The thing is, as you say, if you know yourself well, you don't have to know exactly what it could be, but when you see it, it's just the right thing.
Some things you desire don't really fit you and you want them because you've seen them in others, but in time you realise that that desire was just a stopgap. Chance plays a big role for me. When things are too orderly, when I am precise, I may disregard something that could be dear to me. Where I allow chance, good things happen to me.
I remember when we were children, roaming around the empty fairground looking for lost money. I never found a note because I was looking for it. But if I didn't look, I found money somewhere else.
It works the other way round too. That which we don't want, that too will be fulfilled one day, but sometimes it comes at a price we didn't ask for. Many inner desires come true, but they do not always have only positive effects, but ones that one might not have expected.
The goal orientation that is so often talked about and that one must know exactly what the goals are and how to achieve them, a widespread attitude. On the other hand, nowhere do you get told that you have to learn to distinguish whether the goals are others' or your own, and you run after things that you think you desire or that are held in high esteem. The deception to which one is subject has high potential.
That's another perspective. But even if you don't get what you want, in my experience, you waste less time when you know what you want, because you just look for it, as opposed to looking for anything for a long time and then finding nothing.
I too often leave the store without buying, I'd rather leave empty-handed than with something I don't want.
Maybe it's not about goals specifically, but it is about having a clear direction. Although I admit it's really great when you find that thing you want and weren't looking for. But you can't plan for it.
And chance is always there, whether you plan for it or not.
Yeah, that happens. :) But then again, one spends more days not looking than looking, so it's likely.