I've been also thinking about systems like this, but wouldn't you need constraints and counting? I mean let's say you modeled human behavior based on basic economic principles, then you'd have constrains/rules like:

if money < x, stay home (and you wouldn't meet new people and have an impact)

if money < y, walk instead of taking a bus (and you would get only so far, your reach is small)

if money < z, have no energy to do new things (your behavior would stay the same)

if energy < c, die

edit: adjustments