If you have been training kendo, you may already have heard this. If not, here it is.
Heijoshin: It means the presence of mind.
I can be done here but I would like to keep going a little bit more. :)
There are two parts in Kanji; "Heijo" and "shin". Heijo is ordinary, usual or normal. Shin is as you may know already "mind" or "heart".
So it means you have to keep the state of your mind as it is normally.
However, then, if you are hyper, emotional or energetic all the time, then it may be the normal state of your mind.
Let me break down the kanji "heijo" into two parts; "hei" and "jo". "jo" means "always" or "all the time". And "hei" means "flat". So keep the state of your mind flat all the time.
What does it mean?
Shin or kokoro can be disturbed all the time. Sometimes you get surprised. Sometimes you become afraid. Or you may get panic and you lose your mind.
(These called shikai)
Whenever your mind is disturbed like above, your mind is not stable, i.e., not flat. Thus, heijoshin means "in any situations, you must keep the state of your mind as flat as possible to think clearly and make the right decision".
Well, it is very hard to keep the mind stable all the time as we all know. Probably that is why we have this word to remind us.