Keep Calm in Chinese / Japanese...

失意泰然 is a very old Japanese proverb that suggests “keeping calm and collected at times of disappointment,” or “maintaining a serene state of mind when faced with adversity.”

It's hard to relate individual character meanings to the overall meaning unless you also understand Japanese grammar. The word order is very different than English. That being said, here's the character meaning breakdown:
失 To miss, lose or fail.
意 Feelings, thoughts, meaning.
泰 Safe, peaceful.
然 Like that, in that way, however, although.

Using these definitions in English, we might say, “Although you may fail or lose, have a feeling of peace and calm.”

These two characters mean calm and collected or simply not nervous.

鎮靜 represents the idea of being calm, cool, or relaxed in Chinese, Japanese Kanji, and old Korean Hanja.

My Korean dictionary further defines this as quiet, calm, tranquility, and pacification.
From my Japanese dictionary: calm, quiet, tranquility, appeasement, pacification.

Note: This term is also used in Korean Hanja but there is a slight deviation in the way they write the second character in Korean. Still, a Korean person who can read Hanja, will be able to read this word. We can write it in the Korean form if you wish (just let us know when you place your order). In Korean, this is the word you might use to tell someone to "calm down" or "take it easy."

冷靜 means calm and cool-headed in Chinese, Japanese, and Korean.

Other translations: calmness, composure, coolness, serenity, tranquility.

冷靜 is a good wall scroll for someone that wants to remind themselves to stay calm and level-headed.

See Also:  Sober Calm

安 is used in a lot of compound words in the CJK world.

Alone, this character has a broad span of possible meanings. These meanings include relaxed, quiet, rested, contented, calm, still, to pacify, peaceful, at peace, soothing, or soothed.

安 and even the pronunciation was borrowed from Chinese and absorbed into both Japanese Kanji and Korean Hanja. In all these languages, this character is pronounced like “an.”

虛心 is a Buddhist term that speaks of being open-minded and/or having a calm and humble mind or heart.

腳踏實地 is a four-character proverb that suggests that you should be practical, realistic, and grounded.

Some translate this as a suggestion to be down-to-earth.

The first character means “feet.”
The second means “step on” or “stand.”
The third means “solid,” “real,” or “true.”
The last character means “ground,” “earth,” or “terra.”

Literally, this means “[keep your] Feet Standing [on] Solid Ground.”

少安毋躁 is a short Chinese phrase that means keep calm, don't get excited, and don't be impatient or hot-tempered.

虛心坦懐 is a Japanese proverb that means “with an open and calm mind,” “with no preconceived notions,” or “without reservations.”

In some contexts, it can mean frank or candid.

If you want to remind yourself to approach each situation with no preconceptions, this is a good title for you. This can also refer to the ideas of being candid, frank, and straightforward.

安心 can be defined as relief, peace of mind, feeling at ease, to be relieved, to set one's mind at rest, and easiness.

安心 is a nice word that encompasses great meanings within just two characters. Some of the other meanings include pacifying, settling the mind, and peace of mind. It's also the idea of feeling a sense of security, safety, and confidence in your state of well-being.

This can be used by everyone, but some consider it to be a Buddhist concept (You'll find it in your Zen dictionary).

Note: Can be romanized as Anshin or Anjin in Japanese.

This is a nice word that means peaceful, tranquil, calm, composed, “free from worry,” “public peace,” tranquility, good health, well-being, or welfare in Chinese and Korean.

Note: The definition in Japanese is not so broad but still means peaceful or “public peace.”

安禪 creates a title that means to reach peace and calm through meditation.

安禪 is an excellent wall scroll for your relaxation or meditation room.

This is also a Buddhist-related term that encompasses the idea of entering into dhyana meditation.

This is also used in Japanese, but in modern times, the second character has changed, so it's 安禅 now. If you want the modern Japanese version, just choose a Japanese calligrapher, and let me know when you place your order.

安定 is a word that means: quiet; settled; maintain; calm and orderly; stability; equilibrium.

寂靜 is the Chinese and old Japanese word for calmness, stillness, and tranquility.

In the Buddhist context, this can refer to the calmness of the heart, enlightenment, or the state of being calm and quiet - free from temptation and distress. This can be thought of as being in a state of earthly nirvāṇa.

Note: The second character is written just slightly differently in modern Japanese (静 instead of 靜). Expect a slight variation if you order this from the Japanese master calligrapher. The version shown here is considered the ancient Japanese and original Chinese form.