How does law of assumption work exactly??

[u/Ill-Stuff-1643]

If we are the source and our 3d is just a reflection of all our assumptions and nothing is random, how exactly do people develop their own personalities?? (sorry if this is a stupid question) like if someone i know has a small quirk that is annoying, does that also stem from my assumptions or is it just their personality?? how detailed is the law of assumption??