Yoga Sutra 1.4 Vrtti sarupyam itaratra

“At other times, the seer identifies with the fluctuating consciousness.”
My interpretation of this sutra is a person’s perception of events, life, etc becomes their reality. An example is reading a sad story or book and feeling melancholy afterwards or even depressed. I think the sutra is relating to events beyond just being empathetic to another persons plight but more extreme changes. When the division between surroundings and individual cease to exist the individual takes on the mindset and begins to change behavior, conforming to their current environment. The military forces these behavioral changes upon those entering into military. Almost brainwashing the individual, a process of “breaking down to build-up” therefore creating the solider.
If an individual does not have firm beliefs or trust within themselves they are more susceptible to fluctuations in their actions and thinking. They begin to identify with objects outside of them selves. Believing that happiness can be achieved through objects or achievements, i.e. I will be happy when I finish school, buy a house etc. When the individual attaches to these outcomes they are no longer the masters of themselves and are unable to experience contentment.