Here's to rubbing my two bits on the issue....
Luck has A LOT do with it but if you hesitant too much or over think it, you lose it.
What the masters don't tell you often enough is how many mis-shots or bad shots they have taken before and still do before they finally capture a fantastic one. At times, they re-crop the scene they shot of an average one and turn it into a great shot which they might have caught by luck. Just like your seagull shot. As you were looking at that bird in your viewfinder, were you actually noticing another seagull coming up from the back?
National Geographic photographers in general shoots 1000+ plus shots and choose great one to show the world. But because you saw that shot by so-and-so photographer, you thought "WOW he is so good to capture that shot so perfectly"
You want to improve your chances of getting better shots? That is simple but to capture successfully great shots even over your life time is very challenging. It is like fishing. Some days you come home with a bucket of fishes, another day an empty one and another a big Marlin. Look up famous photographers who shot for decades and you find most are famous for always the same few shots while the rest in their portfolio are great looking but not as stunning as those they are famous for. It happens to the best of us.
As I said, to improve is not hard. Firstly you have to know the fundamental of photography and your camera gear inside out. You should know it so fast that you can picture a shot as you walk and know if your camera is set to take that shot or not. Look at some of the old masters, they can use the same camera year in year out to shoot. Simply because the camera with the same buttons layout, predictable result and function are mastered and drilled into their mind and hands to act naturally.
For example if I am shooting street scene as I walk thru a busy few blocks full of people walking by. Your camera should be set to a shutter speed that can freezes life to some degree of stillness or slight blur to communicate motion. The right focal length to capture full length of top portion of subjects. The right F-stop in case subject is too far or near when you click to ensure subject is still in relative sharpness. Look closely at some of the great shots taken by people, examine it closely and sometimes it is not entirely sharp and might even be a little tiny motion blur. But the subject matter is so impactful that it trump lighting, focus and shutter speed right 'errors'
If i am shooting a scene sitting somewhere like the gentleman I shot in the above photo, I try to look for a relative area I will focus my camera on at all times. So it is easy for me to raise the camera to my eye and shoot or shoot fro my hip level or have the camera on the table or something and just click the shutter. I have adjusted everything and just wait. That means you have to know 'potential stories' that can happen in that area you focus. Yes not all good shots are spontaneous but you can sometime control the situation that increases your chance of capturing something special. Say a fire hydrant with a leak that spray out water spurts unsuspectingly every so often into the path of passing pedestrian. Already your mind's eye should tell you, just focus on that area will capturing you some interesting shots of people walking by and be surprised by a jet of water and how they would avoid it. So you set your camera all ready and wait. And that was what this gentleman in the photo was doing when I went over to talk to him. He is only working the zoom length but his shutter and aperture was all set on manual. He had been sitting there for about an hour shooting people along that narrow street of cafes.
Good photo opportunities are a lot of time about anticipation and/or luck. Which is why photography is such a great life observer and teacher. It teaches you to see things around you and you learn to understand and anticipate before you click. And in the process learn something about life.
But first thing is know your gear well like that back of your hand. And like fishing you have to be patience and quick to react or anticipate. You can only hit something if you don't stop firing. heh.