Fog is always mystical in nature, but you should decide what you want to convey to viewer. As for now you applied three main objects:
- fog
- tree
- bridge
You might make several different shots depending to your likes (meaning your visions). The scenery was laden with good ideas. Wheatfield was correct - you should balance only two things, not these three - they are __not__ complementary here.
I shold stop here, but a few words would help to understand my position.
What about making the tree a main object with a pinch of existing fog, just recalling nostalgic times?
or
The stone bridge has a Mayan style, it's damn heavy. It'd be wonderfully expressed too, but alone and supported by gloomy English moor aspects. Maybe.
Anyway, you presented a good food for thinking, thanks for your lesson. Yes, your picture was teaching me.