pokec0re:

They are the chemical symbols for the neurotransmitters dopamine and serotonin. Dopamine plays in a role in regulation of behavior, motivation, reward, attention, learning and mood. Serotonin plays a role in regulation of mood, appetite, sleep, memory and learning. Together they both directly influence happiness/sadness/depression/anxiety, which are all issues I have struggled with my entire life. These tattoos serve as reminders that my body literally can (and does) make my own happiness. It is also a reminder that under any circumstance I can also choose happiness over anxiety or depression, that I CAN conquer it, and to remember how I have overcome so much in the past year.