I just came across this YouTube video – from one of my favorite photographers/content creators. His name is Craig Roberts, and his channel is called E6. The video’s premise is that if, every time you go out to take photographs, you have a goal (e.g. as in this case red cars) in mind you will see red cars where otherwise you might not. You would see things that you otherwise might miss.
I’d agree with this…up to a point. Yes, you might well see things you would otherwise miss, but you might also miss equally or even more interesting photographic opportunities because you’re focusing so much on looking for your subject.
Maybe a way around this is to spend a morning focusing on a particular subject followed by an afternoon wandering around with no focus to see what you find? Or maybe spend one day on a particular subject and the next day just wander around?