I really like everyone's answers for this. "I'm happy but not fulfilled because I'm still on the way to my dream" stood out to me. I think that the journey towards your aspirations is where you can find happiness and fulfillment, rather than sacrificing your joy in the present moment for hope of a better future. No imagined outcome will ever bring long-lasting happiness, that can only be achieved in the present. So I believe that finding a way to be satisfied with how things are in the present, whether or not you have achieved a certain goal, is the key to being happy and fulfilled.
Besides, what fun is a life where you've achieved everything? You'd have nothing to work towards and nothing would feel special!