Here is an excellent article on Greek Stoicism with nine points to remember as you go about your life which should help you be more productive, creative, and fulfilled. The core idea is one of embracing your challenges as opportunities for growth (some might say the only opportunities for true growth).
One thing that is remarkable is the similarity of Stoic teachings to those of Buddhism. They both place great importance on the idea of being mindful of your thoughts and realizing that they originate from within you, not the circumstances around you, and you are always in control of how you react/relate to these circumstances. Just recognizing unproductive or emotionally-controlled states of mind is a huge first step.
Do you observe any of the practices in the article? How have they helped in your life?