अथ योगानुशासनम् ॥१॥
atha yoga-anuśāsanam - ||1.1||
Now begins the experience of Yoga
Hm... A gentle smile. Then, she proceeded. But, as I observe, what I wanted to observe seems to runaway. I am not able to observe it then.
Haha. Yeah. That is its nature. It is like a classroom of young kids in schools these days. The class will be very noisy, but the moment the teacher arrives, without the teacher doing or saying anything the class settles down. Likewise, as the observer arises, the observed settles down and does not make much noise.
Yoga is the cessation of internal disturbances
स तु दीर्घकाल नैरन्तर्य सत्कारादरासेवितो दृढभूमिः ॥१४॥
sa tu dīrghakāla nairantarya satkāra-ādara-āsevito dṛḍhabhūmiḥ ||1.14||
Correct practice done over long period of time in an interrupted manner is necessary.
अभ्यासवैराग्याभ्यां तन्निरोधः ॥१२॥
abhyāsa-vairāgya-ābhyāṁ tan-nirodhaḥ ||1.12||
Practice and dispassion are neccessary to attain state of Yoga.
Going back to your original question about who will die, it is the observed that was born, that grows and that dies. The observer remains all the time. It is a choice we make on how much we will be with the observer and how much we will be with the observed. The observer only sees and the observed only acts.
द्रष्टा दृशिमात्रः शुद्धोऽपि प्रत्ययानुपश्यः ॥२०॥
draṣṭā dṛśimātraḥ śuddho-'pi pratyaya-anupaśyaḥ ||2.20||
Observer can only observe but is directed by the deeper mind.
श्रद्धावीर्यस्मृति समाधिप्रज्ञापूर्वक इतरेषाम् ॥२०॥
śraddhā-vīrya-smṛti samādhi-prajñā-pūrvaka itareṣām ||1.20||
Sincerity, potency and memory of past mistakes and goal are most important for all practitioners.
I further said that, anything that changes is not part of the observer as someone can observe it changing. For this change to happen, the observed has to be in time. Time then is measured in terms of change. This implies that the observer which is changeless is free of time.
क्लेश कर्म विपाकाशयैःपरामृष्टः पुरुषविशेष ईश्वरः ॥२४॥
kleśa karma vipāka-āśayaiḥ-aparāmṛṣṭaḥ puruṣa-viśeṣa īśvaraḥ ||1.24||
Ishavara is the centre that is free of change and time and therein is neither afflicted by impurities nor is affected by consequences of action.