Dopamine, at least at modest levels, tends to increase the positivity of mood; it tends to make us more outward goal-directed; and it tends to place our body into a state of action ... Dopamine makes us want to move, it makes us motivated, and it makes us think about what's outside us that we want to pursue ... Serotonin tends to activate circuits in the brain and body that tend to make us feel rather placid, kind of blissed, and feel pretty good about what we've got in the present. It tends to restrict our goals toward things that are already in our immediate experience or possession.