Rusty As An Anchor
Turns out, when you don't play CS:GO for a month, you're pretty bad in your first game back. I've got a month to get ready for Quakecon. God help me.
Knowing Your Limits
There's a difference between 'knowing what you don't know' and just plain being negative about your ability to do something. I've never liked the phrase, "I can't"...but there are times when you have to say, "Okay, maybe I shouldn't promise where I can't deliver." That goes beyond the individual level, and sadly I see companies doing it quite frequently. If you're not capable of something, or capable of it within a certain timeframe, don't go making promises. Don't jump in the squat rack with 4 plates when you don't even lift...once you bear that load, if you can't handle it, you're going down and you're not coming back up.
Knowing Your Limits... And Changing Them
It's okay to push yourself...how else do we get better? It's up to you to judge whether you are in a situation that it is okay to test yourself in. Sometimes it isn't up to us, and we are expected to perform regardless of whether we think we can or not. This is trial by fire, and the few emerge from it in victory. Just be sure you don't defeat yourself before you start with a can't-do attitude... you're on this ride whether you want to be or not, may as well lock in and take it like a man.