Confidence boosting phrases - are they effective?

We have all seen the slightly corny "confidence boosting" posters often featuring inspired looking characters and some words of wisdom. Do they really help build confidence or do they actually make people feel slightly nauseous?

I would go for the latter view, I have to say, I think you would have to be a fairly one dimensional and simplistic to actually be motivated by something like that.

Take this quote by Katy Perry for example

"If you're presenting yourself with confidence, you can pull off pretty much anything." 

Really?

Brain Surgeon? Airline Pilot?

It's absurd to think that anyone could carry out these roles just by thinking positively.

However, one quote from Dale Carnegie is actually really useful even though it is decades old.

"Inaction breeds doubt and fear. Action breeds confidence and courage. If you want to conquer fear, do not sit home and think about it. Go out and get busy."

Of all the many books on the subject Carnegie's How to Win Friends and Influence People is one of the most readable once you get over the dated phrases and inadvertent sexism.

Cheers