I advise my students to listen carefully the moment they decide to take no more mathematics courses. They might be able to hear the sound of closing doors. -- James Caballero (This is my bro's fav quote so most probably it will be here forever)

There’s only one idea here; if Gram had the idea, I don’t know what Schmidt did! -- Gil Strang (In his lecture on GS (Gram-Schmidt))

...Cramer's rule is a disastrous way to go because to compute these determinants takes like approximately FOREVER! -- Gil Strang (In his lecture on Cramer's rule and Inversion)

...What ineffable twaddle! I never read such rubbish in my life. -- Dr. Watson, A Study in Scarlet, Sir Arthur Conan Doyle - Me, on the trend of the world toward rubbish paper publication!

So, so, so…what am I trying to say? -- Arthur Mattuck (In one of his ODE lectures)