It has been a proven theory that contentment is the basic requirement to lead a peaceful and happy life. Because, until and unless you put a full stop to your list of goals and desires, you constantly put your focus and effort to acheive them. In the process, you lose the enjoyment of what you have now.
There is also another well proven fact that, until there is aspiration or desire, there is no progress. Even in case of spirituality, only when you have set a goal and work towards achieving it you have progress, otherwise you remain where you are.
So, it is good to be contended with what we have and to aspire for more and to be a part of race that has no end. Well, the secret is to strike a balance between the both, and lead a peaceful life enjoying all the things you have and to keep working for those that you are yet to achieve, so that you keep progressing.
If your discontentment is for your betterment and for the betterment of the others, it is good to be discontent. If you are unhappy about the way things are and aspire to change them and give a new direction, it is good to be discontent. Big people, successful people, great leaders of all times, they aspired for more and did not stop working progressing.
So, cherish and enjoy what you are blessed with now do not have any regrets about them. Think that, whatever you are and how ever you are, it is because of a reason and for your own betterment. Then aspire to become what you want to, accepting the present things, to put your foot towards the future.