54. Don’t be flakey.
If you said you’d do it, do it. If you said you’d be there, go. If you have no intention of doing either, it’s infinitely better to say “no” with an apology than it is to flake out.
Reliability is an important, but humble trait to have. Know that people may not always thank you for being dependable, but no one will hesitate to criticize you for being flakey.