"Those who can, do. Those who can't, teach."
Ummm no. Those who enjoy teaching, teach. Those who desire to pass on knowledge and help to shape the youth of today into future citizens of the world, teach. That quote just instantly diminishes the hard work that teaching is and gives the impression of teaching being "less than."
A slightly better quip (though I'm still not a fan because it just reminds people of the above) is: "Those who can, do. Those who understand, teach." Because you seriously do need to understand the content that you're teaching inside and out to be able to explain it adequately to a bunch of teenagers and to answer whatever questions they throw at you in the process.
Actually, my understanding is this comes from a time when occupations were for more of an apprenticed trades kind of thing. The idea being, you'd spend decades doing woodworking, or sculpting, or whatever it is you did. Then, when the time came that you no longer had the physical capacity to continue doing that which you built a lifetime of experience doing, you would pass it along to the next generation, so they could continue the work.
In the modern world, this saying has no place, however.
"It's only money."
No, no it's not. Someone once said this to me years ago, and I said, "That money represents hours of work I had to do in order to earn it so, *no*, it's not 'only' money."
I've always said that a workplace is somewhere they will hand you green slips of paper in exchange for portions of your life. Your paycheck represents a fraction of your life that will never return. So, it's not only money, it's blood, sweat, and tears.