"If you don't have the time to do it right, when will you find the time to do it over?"
not sure who originally said it; I heard it from Curt Carlson; coach John Wooden is known to have said it; John G. McCrory is known to have said it

"Live in the now."
Buddhist mindfulness

"Only half of programming is coding. The other 90% is debugging."
unknown

"Weeks of coding can save you hours of planning."
unknown

"Without requirements or design, programming is the art of adding bugs to an empty text file."
unknown

"You miss 100% of the shots you never take."
Wayne Gretzky

"Perfection is achieved not when there is nothing more to add, but rather when there is nothing more to take away."
Antoine de Saint-Exupery

"Fast. Good. Cheap. Pick two."
unknown

"Fast. Good. Cheap. Pick zero."
Eljay

"The best reaction to 'this is confusing, where are the docs?' is to rewrite the feature to make it less confusing, not write more docs."
Jeff Atwood

"The best way to get a project done faster is to start sooner."
Jim Highsmith

"The goal of Computer Science is to build something that will last at least until we've finished building it."
anonymous

"Debugging is twice as hard as writing the code in the first place. Therefore, if you write the code as cleverly as possible, you are, by definition, not smart enough to debug it."
Brian W. Kernighan

"There are two ways of constructing a software design. One way is to make it so simple that there are obviously no deficiencies. And the other way is to make it so complicated that there are no obvious deficiencies."
C.A.R. Hoare

"What a single rock star developer can do in a month, can take a team of developers a year in order to fix that damage."
anonymous

"When I started here, all there was was swamp. Other programmers said I was daft to build an application on a swamp, but I built it all the same, just to show 'em. It sank into the swamp. So, I built a second one. That sank into the swamp. So, I built a third one. That burned down, fell over, then sank into the swamp, but the fourth one... stayed up! And that's what you're gonna get, lad: the strongest application on these operating systems."
Monty Python and the Holy Grail (paraphrased)

"Scrummerfall. n. The practice of combining Scrum and Waterfall so as to ensure failure at a much faster rate than you had with Waterfall alone."
Brad Wilson

"The code is hollow--it goes on forever--and--oh my God!--it's full of bugs!"
Arthur C. Clarke's character David Bowman, 2001 (the book) paraphrased

"Bugs hide bugs."
Eljay

"You want to optimize the organization for the people – for the people doing the work – not for the managers. Most large mistakes in organizational design come from putting the individual ambitions of the people at the top of the organization ahead of the communication paths for the people at the bottom of the organization."
Ben Horowitz, The Hard Thing About Hard Things (190)

(I included a couple of my own. Blatant self-aggrandizement.)

After I graduated I learned this lesson fast. It's a great quote about just knowing the tools doesn't make you a craftsman. :-)

“Computer science education cannot make anybody an expert programmer any more than studying brushes and pigment can make somebody an expert painter.” - Eric S. Raymond

These are two of my favorite...

Another Bruce Lee one...

"Don't get set into one form, adapt it and build your own, and let it grow, be like water. Empty your mind, be formless, shapeless — like water. Now you put water in a cup, it becomes the cup; You put water into a bottle it becomes the bottle; You put it in a teapot it becomes the teapot. Now water can flow or it can crash. Be water, my friend."

"Just do it"

I'm not sure who said it, nonetheless, I'm pretty sure it isn't from Shia Lebouf

“There is no programming language–no matter how structured–that will prevent programmers from making bad programs.” - Larry Flon

Another of my favorites

“Live as if you were to die tomorrow. Learn as if you were to live forever” - Mahatma Gandhi

Something that might as well become my motto

And finally one I read today

"You might not think that programmers are artists, but programming is an extremely creative profession. It's logic-based creativity.” - John Romero

When I feel discouraged by the state of the World, I remember this by William McRaven, US Navy Admiral :)

If You Want to Change the World, Start Off by Making Your Bed.

If you make your bed every morning you will have accomplished the first task of the day. It will give you a small sense of pride and it will encourage you to do another
task and another and another and by the end of the day that one task completed will have turned into mini task completed.

Making your bed will also reinforce the fact that the little things in life matter if you can't do the little things right you'll never be able to do the big things right and if by chance you have a miserable day you will come home to a bed that is made that you made and a made bed gives you encouragement that tomorrow will be better.

-- William McRaven, US Navy Admiral

youtube.com/watch?v=3sK3wJAxGfs

"Action is the key to your success" - discovered this many years ago and can't remember who said it, but a quick google just now search seems to suggest this is a shortening of "Action is the foundational key to all success" by Pablo Picasso.

"As a single footstep will not make a path on the earth, so a single thought will not make a pathway in the mind. To make a deep physical path, we walk again and again. To make a deep mental path, we must think over and over the kind of thoughts we wish to dominate our lives." Henry David Thoreau

Nothing in this world can take the place of persistence. Talent will not: nothing is more common than unsuccessful men with talent. Genius will not; unrewarded genius is almost a proverb. Education will not: the world is full of educated derelicts. Persistence and determination alone are omnipotent.

• Calvin Coolidge

The whole quote is good but it's the first sentence that sticks with me.

This is my favorite recent one, by Brendon Burchard:

Or an alternative phrasing I heard from him was: "Don't expect your work to always bring you joy, bring joy to your work"