Proverb: "Better a diamond with a flaw than a pebble without."
Translation: Even when lacking in execution, design with a solid idea will be infinitely more memorable than a bland design that's polished to perfection.

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Proverb: "Be on a horse when you go in search of a better one."
Translation: If you're in search of a better job, you're more likely to find one when already in employment.

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Proverb: "A hasty man drinks his tea with a fork."
Translation: Don't rush through a project thinking the next one that comes along will be better. Every project you undertake can be your best yet. It's up to you to make it so.

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Proverb: "A young doctor makes a full graveyard."
Translation: Equally, a young designer will make more mistakes than an experienced one. It's normal.

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Proverb: "A fall into a ditch makes you wiser."
Translation: Olympic medalists don't win every time, renowned authors rarely win the Booker Prize, and Oscar winners are unlikely to repeat the success. Similarly, designers can't always produce award-winning work, and when the outcome isn't as good as you hoped, there'll still be important lessons learned along the way.

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Proverb: "A bad word whispered will echo a hundred miles."
Translation: Rather than vent about a client, remember that you're the expert, and the client is likely to be unaware of how the design process works. It's up to you to keep the project running smoothly.

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Proverb: "Happy people never count hours as they pass."
Translation: If you find yourself in design employment, counting down the hours until the end of the day, you're either in the wrong profession, working for an idiot, or need to become self-employed.

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Proverb: "A bird does not sing because it has an answer. It sings because it has a song."
Translation: Just as you must hear a song before making a judgment, don't rule-out a design idea before it's been fully explored. Express your ideas in a studio meeting or when brainstorming, even if you're unsure about the effectiveness. It's rare when anyone's first thought is the idea that's chosen.

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Proverb: "A book holds a house of gold."
Translation: No matter how long you've been in the profession, there's always something new to learn. Design books are an incredible source of knowledge.

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Proverb: "A day of sorrow is longer than a month of joy."
Translation: That's how it might seem on a day when things go wrong, but remember, you're doing a job you love. The vast majority can't say the same.

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Proverb: "A wise man makes his own decisions, an ignorant man follows public opinion."
Translation: If you're asked to produce a design based upon current trends, explain to your client why trends should be left to the fashion industry, and why great design is timeless.

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Proverb: "Cheap things are not good, good things are not cheap."
Translation: Designers have a tendency to undersell themselves. Value your skills. You've spent a great deal of time building them.

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Proverb: "Customers are jade; merchandise is grass."
Translation: Without clients, we're designing for ourselves. Treat your clients with respect, because they can be your best salespeople.

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Proverb: "Don't build a new ship out of old wood."
Translation: You might have a stockpile of unused design concepts, but every new client should be afforded the new ideas they're paying for.

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Proverb: "Don't stand by the water and long for fish; go home and weave a net."
Translation: The ideal client won't jump into your lap. Launch a blog. Freshen-up your portfolio. Get out there and market yourself.

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Proverb: "Everyone speaks well of the bridge which carries him over."
Translation: Regardless of experience, if you're asked for design advice, don't ignore the question.

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Proverb: "Forget the favours you have given; remember those received."
Translation: Don't do it because you expect something in return. Do it because it's who you want to be.

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Proverb: "Govern yourself and you can govern the world."
Translation: No matter how busy you are with client work, leave some time for you. It won't do anyone any good if you're too burned-out for work. Reward yourself after a successful project.

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Proverb: "She who asks is a fool for five minutes, but she who does not remains a fool forever."
Translation: It's easy to spot designers with passion — they're the ones asking questions.

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Proverb: "He who hurries cannot walk with dignity."
Translation: Project deadlines (or live-lines) are good for motivation, but if the outcome isn't right, don't force it. Better to spend one more week on a design that will last a lifetime, than spend a week less and live with mediocrity.

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Proverb: "One step at a time is good walking."
Translation: As tempting as it may be to jump straight onto your computer, don't underestimate the value of research, brainstorming, and sketching, when it comes to a complete design process.

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Proverb: "Make happy those who are near, and those who are far will come."
Translation: Concentrate on the clients you have, rather than those you wish to attract, because doing a good job for a good client will lead to more of the same.

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Update:
Authentic, translated Chinese proverbs and philosophies, via @jzy.