知彼知己百戰不殆 is from Sun Tzu's (Sunzi's) Art of War. It means that if you know and understand the enemy, you also know yourself, and thus with this complete understanding, you cannot lose.

This proverb is often somewhat directly translated as “Know the enemy and know yourself, and you can fight a hundred battles without defeat.”

It can also be translated as “If you know both yourself and your enemy, you can come out of hundreds of battles without danger,” or “Know your enemy, know yourself, and your victory will not be threatened.”

決して諦めるな is a Japanese term that informally means “never give up.”

It's also a Japanese way to say “never surrender.”

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

See Also:  Tenacity | Perseverance | Hope

初心忘るべからず is an old Japanese proverb that suggests you try to never forget the enthusiasm you had as a child when you try new things (or even face the day-to-day). Basically, avoid having the mundane attitude that many people get with age.

You'll find this Japanese proverb translated in a few different ways. Here are some of them:
Don't forget your first resolution.
Never forget your childlike enthusiasm.
Forget not the beginner's mind.
Try never to lose your initial enthusiasm (freshness of attitude).

Note: This is sometimes written as 初心忘る可からず. The one shown above is used about 10x more often. There’s only one character difference between the two versions.

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