Spiritimage (I'll shorten that to SI if you don't mind), of course the environment has an influence but in my case it's not so, unless it's overwhelmingly spiritual. The mental environment governs but up to a certain point.
I myself am not totally convinced that restlessness is supported by a demon. According to Yogananda, that's an habit that or mental pattern which, similarly to a rut on a road, costraints the mind along determined actions.
Since such an habit is so die-hard I have this suspicion, without hard evidence, that there is an intelligence, conscious or unconsious, behind it. It must be a malevolent intelligence, since the result is against spiritual evolution. It may be acting consciously, trying his best to keep the mind restless. Or it might be some automatic astral energy, which reinforces karmic tendencies.
If you are interested about the influence of demons on everyday life, I've been ruminating on that. There is a relevant thread on the other forum, which I would suggest you to read before furthering the discussion, there or here as you wish.
http://www.yoganandaji.org/board/showthread.php?t=8792
