On the one hand , if the ambition represents a sort of " motor" it can be very interesting because when you do omething which is very hard , it's always more easier to realize that when you know why you are doing that.For example as far as i am concerned , i want to join a good business school , it's my ambition , however to realize that goal i have to work harder , but even if it will be difficult i know the effects of my work as having an interesting job in the future. Furthermore when you aim an objectif and you success in it , it's make you more confident than beforeand it's help you to preten to an highter one.
On the other hand the risk is to confuse ambition and audacy.Ambition has to be more thoughtful than audacy , audacy is something more ponctual .Using audacy is taken the risk of choosing an unattainable objective and finally fail. Even if the failure is not gravous , you lost confidence and by consequences your futur choice risk to be under your skills.For example if someone wants to be president , he shouldn't follow his audacy by presenting his candidature to the next election, but have the ambition to join a politic school which allow him to enter in the politic world and may be , with time : become president.
On balance we can say that ambition can be positive if follow it at the image of a scale : step by step. "fair and softy goes far in a day"