We get them all the time.
Just that subtle "bump" that pushes you towards something.
Really there are three types:
THE "PUSH BACK NUDGE":
"You're not cut out for this. You're not good enough, fast enough, strong enough, smart enough, etc, etc, etc"
This one is one you don't just nudge back, but you PUSH BACK. It comes from outside your head/other people. The push back nudge is sneaky because it makes you feel like you can't when really that person has just fueled your fire to push you to do exactly what they are saying you can't. So push back, try it, and prove the haters wrong.
The "BLAST-OFF NUDGE":
"I know this seems random, weird, or scary but I think you should give it a try because I really believe it will work out for you"
This nudge is great because it comes from someone you trust or believe in. They are encouraging you to do something you haven't done, something you don't understand, or something you've avoided because they believe it will be great for you. All you have to do is take that nudge and blast off in that direction.
The "LIZARD BRAIN NUDGE":
"I'm not cut out for this. I'm not good enough, fast enough, strong enough, smart enough, etc, etc, etc"
Borrowing this term from the likes of Seth Godin (http://sethgodin.typepad.com) and Trevor Ragan (http://trainugly.com) this is the nudge from inside your head. Straight from your amygdala and holding you back from being someone who kills it at whatever they are doing. Don't hide from it, listen to what it's saying not to do and then do that thing anyway.
We all get them all the time. The question is...what type is it, and how are you going to use it to get better?