When Ross and Rachel were 'on a break!' and he slept with the copy girl...who's side were you on?

Sorry for the long question but I’m curious as to who’s side you were on when Rachel and Ross split up for a night, and he slept with someone that night? And why?
I could probably have made this a simpler question but I wanted the context and have just finished watching said episode
If you need reminding or haven’t seen it then click here