I.13 - tatra sthitau yatnaḥ-abhyāsaḥ

What are the essential qualities of this practice and detachment? Even though the techniques involved are not specified here, the following two Sūtra-s indicate their qualities. 

Practice is the appropriate [and sustained effort to reach] and remain there [in the state of Yoga].

The practices chosen must be learned correctly from and guided by a competent teacher who understands the student in a holistic manner. Owing to the differences in each student’s capacities and potentials, the practices have to be individualised for best results. If the practice is not appropriate for each student, there is little hope of achieving sustained success.