I enjoy collecting quotes: behind each of these, there is a lesson I learned (sometimes painfully). Some quotes by living people are left anonymous, as I'm not sure they would like to be quoted.
On getting things done
Le mieux est l'ennemi du bien. Voltaire
Better is the enemy of good enough.
Nil difficili volenti.
Nothing is difficult to willing people.
The Feynman problem-solving algorithm:
1. Write down the problem.
2. Think very hard.
3. Write down the answer.
Protip: usually people miss step 1.
On dealing with failure
The situation being desperate, everything is now possible.
Success is going from failure to failure without losing enthusiasm. Winston Churchill
An expert is a person who has made all the mistakes that can be made in a very narrow field. Niels Bohr
The brick walls are there for a reason. The brick walls are not there to keep us out. The brick walls are there to give us a chance to show how badly we want something. Because the brick walls are there to stop the people who don’t want it badly enough. They’re there to stop the other people. Randy Pausch's Last Lecture
See also: We are sorry to inform you... (required reading before reviewing) and The importance of stupidity in scientific research.
On writing
What is written without effort is in general read without pleasure. Samuel Johnson
Write a paper so that at least you yourself are able to read it five years from now. Jerry Marsden
I didn't have time to write a short letter, so I've written a long one instead. Pascal
Prose is architecture, not interior decoration. Hemingway
On publishing
If you try to talk to two people at the same time, you end up talking to the wall. Professor at Caltech
Don't scoop yourself. Professor at Caltech
Don’t worry about people stealing your ideas. If your ideas are any good, you’ll have to ram them down people’s throats. Howard Aiken, IBM engineer
On the nature of genius
Genius is 1% inspiration and 99% perspiration. Thomas Edison
Se la tua idea geniale non l'ha mai pensata nessuno, è probabilmente una minchiata. Enrico Pagello
If nobody had ever thought your genius idea, it's probably worthless.
Che cos'è il genio? è fantasia, intuizione, decisione e velocità d'esecuzione. from Amici miei
"What is genius? It's imagination, intuition, willingness and speed of execution." This is spoken in the movie Amici Miei referring to a rather crude practical joke, but it applies equally well to research.
On design
Il semble que la perfection soit atteinte non quand il n'y a plus rien à ajouter, mais quand il n'y a plus rien à retrancher. Antoine de Saint-Exupery
It appears that perfection is achieved, not when there is nothing more to add, but when there is nothing left to remove.
On modeling and abstractions
The best model of a cat is another cat, or better yet, the cat itself. Norbert Wiener or Arturo Rosenblueth
The price of metaphor is eternal vigilance. Norbert Wiener
Signals are not data,
data is not information,
information is not knowledge,
knowledge is not understanding,
understanding is not wisdom,
wisdom is not truth,
truth is not beauty,
beauty is not love,
love is not music,
music is the best!
Clifford Stoll + Frank Zappa
A good man knows his limitations. Harry Callahan
Relayed by a professor in Sapienza University, and valid equally well for estimation and control.
See also: Respect the unstable
On data-based science
If you torture data sufficiently, it will confess to almost anything. Fred Menger
On teaching
La cultura è l'abitudine del pensare chiaro e logico, il coraggio del giudizio indipendente. G. Salvemini
Culture is the habit of thinking clearly and logically, and the courage of having an independent judgement.
On robotics
Never antropomorphize robots --- they hate it.
Not sure about the attribution; I've read a similar one (with "computers") from Michael Ernst.
The Three Laws of Roboticists:
1. Never give a robotic demo.
2. Follow your advisor's advice, except when it contrasts with the first Law.
3. When the demo fails, protect yourself by blaming the batteries.
On programming
The competent programmer is fully aware of the strictly limited size of his own skull; therefore he approaches the programming task in full humility, and among other things he avoids clever tricks like the plague. Dijkstra
On lab safety
Always keep one hand in the pocket. Professor at Sapienza University
This is all I remember from a course on control of electric motors a few years back, but it is really good advice.
Explanation: when you work around machines that operate
with industrial currents, one day you will screw up and touch something you
were not supposed to touch. If you are touching the apparatus with two hands,
chances are that current will flow from one hand to the other, through your
heart, and you'll probably die. If you are touching with only one hand, at most
you will get a "kick" and a slight burn. So, in doubt, always keep one hand in the pocket.