When push comes to shove, particularly these days, people will wear whatever size watch they want to. That's fine, if your happy that's all that actually matters. No one should or indeed can tell you otherwise.
The golden ratio is a decent starting point for getting a size but there are other aspects that affect how a watch is perceived on the wrist. Such as how flat, or rounded, your wrist is, how big your hands are and where on your wrist you wear the watch. Me being an old traditionalist when it comes to watches, I wear mine to the arm side of the end of the Ulna.
Two other rules you can go by are that the watch face, including lugs, should ideally cover no less that 70% of your wrist width and no more than 85%. Secondly the lugs should never touch or overhang your wrist. If they do, then it really is too big, they should sit in from the edges of your wrist.
Working with those three rules is just what was considered "tasteful" but it's all subjective, fashion has blown all of that out of the water these days. I personally hate oversized watches and I think a big watch on a small wrist, or indeed a small watch on a big wrist, looks ridiculous. But that's just me, everyone has different opinions.
That being said, I've also had to break all of the rules myself for the Apple Watch.
My wrist is 75mm across and even with the Milanese loop adding a little extra height, with it's lugs bringing the height of the watch up to 48mm. That's still only 64% of my wrist width, so going by the above standards the Apple Watch would be 6% too small for me.
I do actually agree with that though, when I look at it, it does seem fractionally too small for my wrist and I'd be quite happy if Apple were to introduce a 46 or 48mm watch in the future.
At the end of the day there's only one true way to tell if a watch of any kind is right for you. Try it on. If it looks too big, it probably is, likewise if it looks too small. It's a sort of three bears kind of situation
