Dopamine is just one of many neurotransmitters that your brain (and gut) release which affects your mood and outlook. Dopamine is one of the most important because it is perhaps the singular neurochemical responsible for our good habits. Dopamine is the “reward” that our bodies release after we do something that feels good, or we accomplish something that we are proud of achieving. You get a dopamine dump when you exercise, when you have sex, meditate, and even when you breathe correctly, among other actions.
Dopamine is also why people get addicted to drugs, seeking higher and higher levels of the neurotransmitter to feel the same “high,” but destroying their dopamineric pathways along the way.
Dopamine is released via the dopaminergic pathway, sets of projection neurons that release dopamine. These neural pathways lead out from the mid-brain, working out to other parts of the brain along synapses.
Dopamine leads to more physical (and mental) movement. Less movement is caused by a lack of dopamine. Parkinson’s patients, in fact, usually show a depleted level of dopamine. This is why Parkinson’s sufferers move slowly and speak slowly.
Too much dopamine in the brain can cause schizophrenia, hallucinations, manic feelings, and anxiety. All addiction is driven by dopamine. Even your need to check your Facebook status is driven by the release of dopamine.
In less severe instances, those who feel bored or feel apathetic usually have too little dopamine. The right amount of dopamine can, however, lead to feelings of bliss, and even a flow state as described by meditators and athletes.
Fortunately, you can find your dopamine “sweet spot” naturally, simply by practicing a few breathing exercises. 
Why Deep Breathing Increases Dopamine
When you practice deep breathing (also known as belly breathing or diaphragmatic breathing) you are using your diaphragm, instead of shallowly filling the lungs and exhaling. The movement of the diaphragm down and its subsequent contraction to expel all the old, stale breath from your lungs triggers the brain to release dopamine. Shallow breathing does not do this.
Yogic breathing often starts with deep breathing for this very reason. Just practicing deep breathing for five minutes can calm the nervous system and start to initiate the release of the “reward molecule” that inspires a calming of the nervous system.  
When you are stressed, you tend to breathe shallowly, which forms a negative feedback loop, reducing the amount of dopamine released by your brain, thus increasing the feeling of stress and discontent.
As clinical neuropsychologist Kristoffer Rhoads, Ph.D. explains, your breathing tends to be irregular when you are anxious. This means your chest cavity only expands and contracts in a limited way, which then reduces the signal to you brain and nervous system to release calming and happy-making hormones like dopamine.
Additional benefits of deep breathing include reducing physical pain, boosting your mood, and even allowing you to perform athletic feats more easily.
To practice dopamine-inducing breathing, simply sit tall and rest your shoulders down, away from your ears. Take a deep breath in through your nostrils, allowing your belly to expand so that the diaphragm can drop down and the lungs can expand into your torso. When you exhale, draw the diaphragm in and up so that all the air can be expelled from your lungs completely. This process should be done slowly, without force. Practice for ten to fifteen breaths to allow your dopamine levels to find a “sweet spot” in your body.
 Dopaminergic pathways. (2004, May 22). Retrieved from https://en.wikipedia.org/wiki/Dopaminergic_pathways
 Ma, X., Yue, Z., Gong, Z., Zhang, H., Duan, N., Shi, Y., … Li, Y. (2017). The Effect of Diaphragmatic Breathing on Attention, Negative Affect and Stress in Healthy Adults. Frontiers in Psychology, 8. doi:10.3389/fpsyg.2017.00874
 Kressin, N. A., Nielsen, A. M., Laravuso, R. B., & Bisgard, G. E. (1984). RESPIRATORY EFFECTS OF DOMPERIDONE – PERIPHERAL DOPAMINE ANTAGONIST. Anesthesiology, 61(Supplement), A468. doi:10.1097/00000542-198409001-00468