Not too sure how I feel about this one, on the one hand I think everyone should be as ambitious as possible, and try and better themselves in any way they can.
On the other hand, it is also true that being content with who we are and what we have is extremely important. Striking a balance between these two should be the key, and I believe doing this comes with age and experience.
For example, when I was young I went through phases of wanting to become a footballer, rockstar and Formula 1 driver - sadly none of this worked out, but I'm not too bothered! The child me would be devastated at the thought that none of these pipe dreams came true, but to be honest I'm quite content with who I am at the moment.
That's not too say that it's wrong to have insecurities, or to improve yourself. Everyone is insecure about something, that's a fact of life.
So, yes I do believe it's important to be ambitious, but I also believe it's important to stay grounded. Trying to have the 'perfect life' according to the media, celebrities and popular culture may make you feel 'secure', but it probably won't make you happy.