Brazilian Tangerine Quartz is a beneficial crystal to work with to restore optimism and balance fluctuating moods.
As a fertility crystal, it will also guide you to tune into reproductive cycles to create more harmonious wellbeing. 
It is a crystal of joy and pleasure and will guide you to define what that looks and feels like in your life, and to make changes accordingly for your vision or intention to materialise. 
It reminds us that fertility is also in all the creative aspects of our being and our surrounding world.