Composition: a fascinating subject. I've studied some of the artists of the Italian Renaissance, who 'constructed' their pictures on mathematical principles ('golden section', etc). It was all very new to them, and some artists seemed more interested in the mathematics than the painting!
'Good' composition is a personal thing, yet there's probably a consensus about what constitutes a 'satsfying' arangement of elements within a picture... just as most of us can recognise harmony in music, and differentiate it from dissonance. Dissonance is fine... in small doses. Eccentric composition is fine too... in small doses. We quickly get weary of atonal noodlings (some modern jazz, for example
) and wilfully oddball photographs.
When I'm out in the landscape, I let my subconscious mind take over. I don't think about composition, or camera functions, or anything much at all. This allows me to be 'present', in the 'here and now', simply enjoying what happens next. Photography becomes effortless, an extension of seeing. Composition takes care of itself. Yes, i know, it sounds like hippy-dippy nonsense, but it works for me.
When I'm 'in the zone', I take pictures. When I'm not, it's hard work. And I know which state of mind produces the better pix.
So, for me, composition is retrospective, something I notice when i'm reviewing pix on the computer screen.
The 'rule of thirds' is a useful starting point... but it's a blunt instrument. It's fun to play with accepted notions of composition... like having the subject at the edge of a pic, or dead centre. Or having someone who appears to be looking
out of the picture space, rather than
in. Etc...
There's plenty of material 'out there' about the emotional impact of picture composition: well worth a read.