Our brain works through the hormonal mechanism  called neurotransmitters which send messages to other neurons,triggering certain reactions expressed in our moods unconsciously. In some situations we feel good,bad,depressed,excited,focused,stressed,elevated,confident,satisfied,happy or unhappy.All these moods are regulated by the presence or the absence of neurotransmitter’s activity in our brain. Main neurotransmitters and their fonctions can be summarised as follows :

DOPAMINE : When you orientate yourself towards a goal that is dopamine which motivates you. Dopamine is the hormone, released when you get something, reach a goal, achieve some target. It starts releasing when you think your reward at the end of the envisaged action. With dopamine you feel so great and elevated. Its function is to motivate our brain to survive ,having the necessary resources for life. When there is no dopamine you feel low motivated,pessimist.

SEROTONIN : When you are praised,respected and accepted by your social counterparts,your neurons release serotonin. It fills you with pride and confidence. It is a hormone of approved social respect whose function is to moderate relations in a group ,analysing behavioral signals coming from other group members about the position and status of the one’s own,helping him to understand threats and opportunities inside a society. When there is lack of serotonin, you feel alienated and depressed.

OXYTOCIN :Oxytocin helps you creating social bonds. Trusting,loving your partner,family members,lover,friend etc. When you loved,cared,trusted,caressed,touched  and do the same interactively,your brain releases oxytocin.When oxytocin is lacked,you feel alone,worried and left aside.

ENDORPHIN : Endorphin helps you to mask your pain. That can be physical and social pain which endorphin helps you to cope with. Physical exercise,laughing,crying can cause your brain to release endorphin.If you lack endorphin,this can make you agressive,easily irritable and reactive.
So these are the happy chemicals whose functions are to help you to sustain your well-being. These are the chemicals of survival and healthy life. If your brain gets signals of danger,threat, pain and problem, your brain releases 

CORTISOL what we call as pain. It makes us feel bad and motivates us to do something now.A steady stream of cortisol leaves you feeling you must do something to avoid disaster. When your brain releases cortisol somehow, it means that releasing your happy hormones are inhibited. If you release happy hormones,it means that you are in a situation far from threats and dangers, namely in you are in a well-being. Only in a well-being you can get your self realisation,being productive,creative and cooperative,focusing your energies to increase your happiness or at least to keep your mood at top.