Another looming point for discussion

Do those who settle for less often often underachieve?

I am a person who tried to make the most of what I have.But often I see people who are content with what they have ,hesitate to take on an aggressive personna and go on to achieve what they want.Sort of the side effects you would find with the overdose of self confidence ,mostly found in qualified professional i presume,that tends to instill the ideology ,that 'Im prepared to take on anything'.Blame it on corporate pressure or the deadline theories,It does have its pro's and con's though.