I ran into an old friend this weekend, and wow! The dude has gotten into serious shape.

He’s been working out five days a week for the past year and half, it turns out. Crossfit. And he looks great—trim, lean, and muscular. Reader, if you walked past my friend on the street, you’d think to yourself, “I bet that guy works out 5 days a week.”

Our level of physical fitness is obvious. We get a daily report when we look in the mirror each morning, and we’re either where we want to be or not. We’re forced to confront our status daily.

College students hate group work.

I hear plenty of griping from my students about group projects and group presentations, and I have to admit: I felt the same way at their age. Depending on others is hard! Can’t I just do it myself?

But we all discover the same thing once we enter the working world:

All work is group work.

The idea of the lone wolf—Sorry, I work alone—may be romantic, but it’s a fantasy. Now, more than ever before, our success depends on our ability to work with others. Instant worldwide connectivity has made sure of that. And what makes a person good at working with others? A few traits:

What can you do with 3 inches of dental floss?

Not much.

A 12-inch length of floss is 100% useful relative to its intended purpose: cleaning between your teeth. It’s long enough to wrap around your fingers a few times, so it makes the job easy (or as easy as possible, because every time I floss I think, “Am I doing this wrong? Why is this so hard?”).

A six-inch length of floss is maybe 40% as useful as a foot of floss. It’ll work, but awkwardly—six inches of floss is not quite long enough to get a good grip.

One of the best habits I’ve picked up in the last few years is sending a handwritten thank-you note when someone does me a favor or goes above and beyond in some way. It’s one of those little habits that requires very little effort but is very effective.

Here are three quick reasons to consider writing regular thank-you notes!

1. It’s quick and inexpensive

Writing and mailing a thank-you note takes roughly 5 minutes and costs about a dollar (including postage). If you keep a package of them in your desk drawer (I use these from Amazon), you can fire one off in less time than it takes you to walk across the office for a cup of coffee.

I usually read around two books a month, but I haven’t finished a book in almost three and a half months. I’m currently stuck on a great book: Jonathan Haidt’s The Righteous Mind: Why Good People are Divided by Politics and Religion. It’s a dense, well-researched volume, and it takes a lot of concentration to read well. I’m committed to finishing it, but I haven’t made it a priority.

A regular reading habit is central to personal development, and the effects of stopping are noticeable. My brain feels malnourished and slightly atrophied. I’m reminded of something Jim Rohn used to say: “Some people read so little they’ve got rickets of the mind.” That’s a great metaphor.