Dopamine is an extremely powerful chemical produced by the nerve cells in our brain. When it is released we momentarily feel happier but when it dips we can feel low and deflated and search again for that initial high, sometimes in unhealthy or unhelpful places.
Here is a one page summary of how Dopamine affects us. The main themes are taken from the following inspiring book:
Habits of a Happy Brain: Retrain Your Brain to Boost Your Serotonin, Dopamine, Oxytocin, & Endorphin Levels by Loretta Breuning
Do get in touch if you'd like help to get that buzz from things that are good for you.