Dopamine is a well known but commonly misunderstood neurotransmitter. It is responsible for the anticipation of a reward, however not the reward itself. Very closely linked to pleasure and desire, dopamine has a wonderful sensation. For our ancestors it was vital to fuel our desire to survive. For instance if you were hungry and there's a tree with mangos, but the fruit is very high up the tree. Dopamine will release in the amount equivalent to the nutrition the mangos will provide. Negative neurotransmitters and hormones will release the equivalent of the height of the tree, the scarcity of food, and how skilled you are at climbing.
Positive Neurotransmitters and hormones V.S. Negative Neurotransmitters and Hormones
Positive > Negative = positive action
Positive < Negative = negative action
(Positive = Negative) = indecision
This results in you either climbing the tree for the mangos or trying to find a smaller tree. This was very vital for our survival and is the basic way we figure out if something is good or bad for us. If we didn't have cortisol in this equation we would constantly take risks that would lead to our deaths, as well if we didn't have dopamine in this we would have panic attacks constantly. The way dopamine is used nowadays has taken a different role for us, as food and clothing are widely available, and our grasp of the future has wildly grown. In today's world it is centered more on actions unrelated to hunting, gathering, or building a shelter for yourself. Now we go to work and get a paycheck. That pay check is the promise of money, however you have to wait a week or so to get paid. But we have the notion that we will get money. This can fuel us to continue to do hard work. So the question we all get to decide is how much time is worth how much money. The dopamine in our system puts a value on that paycheck and releases according to the amount of pay and work environment. Your cortisol will put a value on how hard the work is as well it will put a value to what you lose from working. If you have a decent amount of dopamine in your system then things work out well. You feel happy even if you are enduring a moment of stress in your day. The same is true if you don't value your time highly. If imbalance is negative then you quit your job eventually and the dopamine and serotonin levels are low.
This is different for other animals however. Their mindset doesn't have the ability to stay in a place they don't want to be in. Most animal brains are based solely off of the influx of the neurotransmitters. If a lion is chasing a zebra, the lion will stop chasing as soon as cortisol is more prominent than dopamine. While we have the ability to keep chasing and still attempt to catch the zebra. With humans, we have the ability to set our own threshold of action. That's why we have the ability to overcome anxiety. We also have the ability to focus only on the possibility of positive outcomes. Such as getting the mango or getting a better job. This is how our primitive use of dopamine comes into place. Dopamine is used as a filler because the main reason for neurotransmitters was to survive. How much we value objects, people, places, all become abstract and have nothing to do with survival. Let's say you are quite affluent and you are able to buy a big house, nice cars, a boat. The amount of money you have is only important if it is too low. Same is true with food, shelter, transportation, etcetera. Abundance leads to habituation. Habituation is the process of having something so constantly that it means less and less. If you make a hundred thousand dollars every year. It becomes meaningless to make an extra thousand. However if you make thirty thousand dollars a year an extra thousand is pretty important. This applies for virtually every constant experience that we have. It leads to taking objects, people, and places for granted. It also becomes critical for our identity, without this constant influx of neurotransmitters we would feel off. Such as an alcoholic not being able to drink or a cigarette smoker not being able to smoke. This creates a cycle of producing happiness in great quantity (at first) when you do the action, then anxiety when you don't have access to the action.
Our mind has a very ridged world view and your place in it. Anything can offset your sense of normalcy and habituates have a very big part to play in this. If it is normal to meet random people then you have a desire to do so. If you don't normally enjoy meeting new people then you won't do so.