Shraddha: Faith, devotion
Samadhi: Perfection, culmination of something
Poorvak: With the aid of, by
Sage Patanjali goes on to detail more sanskars that remain before reaching the state of virampratyay.The other sanskars (besides that of videhprakritilay) include attaining the samadhi (perfection) in shradhha faith and devotion), veerya (potency) and smriti (remembrances) with the aid of pragya (intellect).
Yoga is a perfect and precise science. It calls for 100% faith and devotion, and priority over other things. This keeps one motivated to not dissipate his/her force in mundane activities, and generate the potency/tej/veerya, which fuels the onwards journey. These then lead to purification of memory, a memory which reminds the sadhak of his/her purpose, the cycle of pain and pleasure in which he/she was caught, and the reality of Creation. All this happens, while the mind/intellect is active