If you’re feeling sad, hopeless, unloved, unappreciated, unmotivated and less excited, it’s likely that you have a dopamine deficiency. To compensate for the deficiency, the mammalian brain generates a craving for behaviours that activate the dopaminergic system.
The dopaminergic system is basically the brain’s reward system and plays a central role in establishing your mood.
Dopamine is a “feel-good” neurochemical that serves as a motivational signal in the brain. When you anticipate a reward or engage in goal-directed behaviours that are associated with rewards, dopamine levels tend to increase.
This anticipatory increase in dopamine acts as a signal that motivates you to seek and engage in certain behaviours that you know may lead to the reward. Because you felt rewarded in the past.
For example, research has found that the dopaminergic system lights up when people eat their favourite foods,  N Volkow et al (2010) or what has been described as “comfort foods”.
A 2020 paper published in the journal Physiology & Behavior  further discovered that the brain has “hedonic hotspots”  — subregions that amplify satisfaction and can stimulate your motivation to seek out activities or things to consume which give you sensory pleasure.
“Our frequent human tragedy is that the more we consume, the hungrier we get. More and faster and stronger. What was unexpected pleasure yesterday is what we feel entitled to today, and what won’t be enough tomorrow.” [Wounded Ruler; gluttony, greed, lust etc]
~ Robert Sapolsky, Behave: The Biology of Humans at Our Best and Worst, p.83, (2017)
The problem with dopaminergic urges is that we grow resilient to them. Once rewards are learned, dopamine becomes more about his anticipation or reward rather than the reward itself.
This can result in one of two behaviours. The body stops producing dopamine and you risk becoming depressed. Or your craving can’t be satisfied so you up the dosage or consume more in a vain attempt of stimulating the pleasure you crave.
Dopamine makes you feel motivated to move towards things that don’t actually satisfy you anymore but you still crave more of it because past experiences have raised your expectation.
Because a habit is associated with satisfaction — a survival mechanism that worked in the past — dopamine discharges make it difficult to stop performing an action that you perceive will deliver sensory pleasure.
That’s because dopamine reinforces learning and conditioning. It helps the brain learn which behaviours are associated with positive outcomes and reinforces those behaviours.
Dopamine release strengthens the neural pathways associated with that behaviour, making it more likely to be repeated in the future. So it’s important to recognise specific habitual behaviours you believe will lead to a reward.
One way to do this is to recognise when you do not feel rewarded by a “comfort” behaviour. Irrational guilt surfacing from the Self is also an internal message that a particular behaviour is no longer providing you with any value.
This anomaly of dopamine can be seen in various examples of certain behaviours that portray intrinsic motivation and extrinsic motivation. You will probably also recognise when you do things that are driven by dopamine rather than an actual need.
Essentially, dopamine binds you to an attachment whereby you feel you are entitled to and deserving of a reward (Lover). But when you build resilience to it, you no longer feel satisfied.
Subsequently, you feel sad, frustrated, hopeless, low-energy, less excited etc. Studies show a correlation between depressive moods and low dopamine levels. 
You can read an example of this from Greek mythology in the story of Tantalus.
It’s clear to see how dopamine is implicated in addiction. Substance abuse and certain behaviours, like gambling, emotional eating, promiscuity and sex addiction, shopping, working out etc, can lead to excessive dopamine release that reinforces addictive behaviours that can prove to be destructive rather than constructive.
Over time, individuals may become motivated primarily by the anticipation of the substance or behaviour that triggers dopamine release rather than the actual value or pleasure meeting your goal delivers.
In addition, dysfunctions in the dopamine system have been linked to motivational disorders, such as depression and anhedonia (a reduced ability to experience pleasure).
In these cases, individuals may struggle to find motivation to engage in rewarding activities. You, therefore, need to understand how your motivation is being triggered and identify whether the perceived need is constructive or destructive.
If you are suffering from anxiety and depression or overcoming emotional wounds that rely on nurturing emotional wellbeing, check out our article titled: Nurturing Emotional Wellbeing To Overcome Anxiety and Depression.