I have to admit that I am not sure what would be the best Latin translation for the English phrase "Everything is a matter of..."...
The meaning is close to: "Everything depends on...". Am I right?
If so, how about "Omnia ex animo aequo, spina erecta et corde quieto pendent", dear?
Your suggestion is very good, but in this way we miss "to keep" which is, in my opinion, quite important. You know, it's something like: Everything depends on the fact that you always keep mind quiet etc., even in difficulties.
You're right, Efee. My proposition doesn't quite convey the source. Ok, let's leave your version, dear. I will only replace "serenum" with "aequum" since you like it.