I Am Strong in Mind in Chinese / Japanese...

気の強い means strong-willed or strong of heart in Japanese.

Here's the character breakdown of this Japanese title:
気 (ki) spirit; mind; heart; nature; motivation; intention; feelings; essence.
の (no) possessive particle.
強い (tsuyoi) strong; powerful; mighty; potent; resistant; resilient; durable.

Note: Because this selection contains some special Japanese Hiragana characters, it should be written by a Japanese calligrapher.

強壯的身體堅強的心態 is the Chinese phrase for “Strong Mind, Strong Body,” however, the character order is actually “Strong Body, Strong Mind,” as that's the more natural word order in Chinese.

強い体強い心 is a way to write “strong mind, strong body” in Japanese.

Each of the two lines starts with 強い (tsuyoi) which means: strong; powerful; mighty; potent; resistant; resilient; durable; tough; stiff; hard; inflexible.

The body is represented with 体 (the ancient version is 體, romanized as karada), which means: body; build; physique; posture; torso; trunk; health.

Mind is represented with 心 (kokoro), which can mean heart, mind, or soul, depending on context.

強い體強い心 is not a common phrase in Japanese, so it's not the most natural title for calligraphy. In English, you might want to write it, “strong mind, strong body” but, “strong mind, strong body,” is more natural in Japanese.

Note: Because this selection contains some special Japanese Hiragana characters, it should be written by a Japanese calligrapher.

不動心 is one of the five spirits of the warrior (budo) and is often used as a Japanese martial arts tenet.

Under that context, places such as the Budo Dojo define it this way: An unshakable mind and an immovable spirit is the state of fudoshin. It is courage and stability displayed both mentally and physically. Rather than indicating rigidity and inflexibility, fudoshin describes a condition that is not easily upset by internal thoughts or external forces. It is capable of receiving a strong attack while retaining composure and balance. It receives and yields lightly, grounds to the earth, and reflects aggression back to the source.

Other translations of this title include imperturbability, steadfastness, keeping a cool head in an emergency, or keeping one's calm (during a fight).

The first two Kanji alone mean immobility, firmness, fixed, steadfastness, motionless, and idle.

The last Kanji means heart, mind, soul, or essence.

Together, these three Kanji create a title defined as “immovable mind” within the context of Japanese martial arts. However, in Chinese, it would mean “motionless heart,” and in Korean Hanja, “wafting heart” or “floating heart.”

有志者事竟成 is an old Chinese proverb that has been translated many different ways into English. As you read the translations below, keep in mind that in Chinese, heart=mind.

Nothing is impossible to a willing heart.
Nothing is impossible to a willing mind.
Nothing is difficult to a willing heart.
Where there is a will, there is a way.
Nothing in the world is impossible if you set your mind to doing it.
A willful man will have his way.
If you wish it, you will do it.
A determined heart can accomplish anything.
All things are possible with a strong mind.

精神力量 is a title that speaks of one's soul or spirit and the capacity or strength that soul possesses.

The first two characters mean mind, heart, spirit, and/or soul.

The last two characters mean strength, capacity, or ability.

Note: Separately, these are two words in Japanese and can be pronounced, but this does not make a natural title in Japanese (best if your audience is Chinese).

This can be translated as unwavering determination, unwavering resolve, or strong determination.

堅定 means unwavering, firm, steady, staunch, and/or resolute.

決心 means determination, resolve, resolution, determined, firm and resolute, or to make up one's mind.

If you want a longer version, 堅定不移的決心 is also a popular phrase with a similar meaning. Contact me if you want that instead.

寂 means silent, solitary, quiet, calm, still, rest, or tranquil.

This also has a strong association with Buddhism where it can mean “entering into Nirvana.” In that context, this is sometimes used to refer to the passing of a Buddhist monk (he is silent, as he has entered Nirvana). For the living, this is about tranquility (especially of mind).

Some will also use this to mean “elegant simplicity.”

From Sanskrit, this can represent praśama, vivikta, śānti, or nibbāna (nirvāṇa).

思い切り can be translated as “with all one's strength,” “with all one's heart,” “to the limits of your heart,” or “to the end of your heart/emotions.”

The character breakdown:
思い (omoi) thought; mind; heart; feelings; emotion; sentiment; love; affection; desire; wish; hope; expectation; imagination; experience
切り (kiri) bounds; limits.

Note: Because this selection contains some special Japanese Hiragana characters, it should be written by a Japanese calligrapher.