mental operations

1. "to orbit around the earth" -- I think "orbit within coordinates" does not go well with each other.
2. "mental operations" is difficult to understand for me in this context. Maybe thoughts might orbit around a problem...?

The premonition that both marriage and adultery stay on their predetermined orbits has rather discouraged me.

Kajjo

I can suggest:

Premonition that the marriage as well as adultery operates within predetermined parameters, like some thought processes do, has rather discouraged me.

However I don't really get what the author is trying to say!

Here's the context but I don't guarantee it will clarify things:

Namely, they are both masked in their opositions - pure feelings, so we supposedly honourably love our wife and we are crazy about our mistress, while both of them do not mean to us more than a deodorant or watermelon, they refresh us one from another, one for another.

Indeed, that does not clarify much, I'm afraid. I do not understand the first part at all and I can not see the connection with the orbits.
Maybe the second sentence could be rephrased as:
Supposedly, we truly love our wife and we are crazy about our mistress -- while in reality both do not mean more to us than a ...
Kajjo

Forgive me if I'm wrong but this doesn't seem to be the context for the original idea of 'orbiting' and 'mental operations'.

You know well, Florijan, that I did not always give your emotional philandering nor even your coming back home the evil eye. I was actually simply dejected by a thought that not in a single relationship of the kind, lawful or unlawful will there be any incidents. Premonition that both marriage and adultury stay on their predetermined orbits like some thought processes do, has rather discourage