So far, what we know is that some hormones play a part, like dopamine, testosterone, and estrogen. Dopamine is linked directly to reward systems and feelings of accomplishment, while testosterone has been associated with confidence and assertiveness, and estrogen is associated with empathy and emotional intelligence.

Yeah it's sad that, sometimes we put all the blame on people for being lazy, not hardworking enough, or we don't understand why they have all those negative thoughts and low energy, when in fact their system's just not working properly. Like, we can't expect a person with a torn tendon to lift much weight, but we expect everyone to try and be accomplished as if it all depends on them.