1.4 At other times, the seer identifies with the fluctuating consciousness
[from BKS Iyengar]
The ‘other times’ referred to here are the times when we are not practising yoga, or are not seeing things as they really are (because of the kleshas or afflictions, such as jealousy, anger, fear, etc). When we are not aware of the true nature of things, we are caught up in sensory experience, the thoughtstream, and even identify ourselves with those thoughts and experiences, not seeing ourselves as distant from them.
As an example, let us imagine that we notice a thought in our heads which states that we are not good at such and such an activity. We may start to believe this as a fact, rather than just notice it as a construct of our minds. Then, when we next do such and such an activity, this thought may actually influence our ability to perform the task. Both yogic and Buddhist philosophy argue for the need to detach ourselves from our thoughts, that we are not those thoughts, we just have the thoughts. The thoughts are not us, just in our heads. Of course, it is not always easy to gain this distance from our thoughtstream / memories / sensory experience, but the path to doing so is that of the eight limbs – asana, pranayama, meditation, the yamas and niyamas (coming soon!).