I read some place a while back that Isis is not an old Goddess of Egypt. Rather her roots go back to Nubia, a nation that existed before Egypt became a strong nation.
And Isis is an English transaltion of the Greek translation of Esat (pronounced EE SA)
M....We all go through phases. We doubt either some or all of what it is we think we believe. From what I've seen in the past, it always seems to happen around late fall and winter months.
Personally, I think it may be that as the weather chills off, we spend less time out side. Less direct connection with nature.
When was the last time you went bare foot in the yard?
Take some time for your self. Go for a walk in the woods, sit by a tree or flowing water, and just enjoy the place you're at.