तत्र स्थितौ यत्नोऽभ्यासः ॥१३॥
tatra sthitau yatno-'bhyāsaḥ ॥13॥
tatra = here; there; so that
sthitau = resolutely; continuously; constantly;
yatna = effort; practice
abhyāsaḥ = cheerfulness; assiduousness
Assiduousness means resolutely adhering to one’s practice of yoga. ||13||
PATANJALI YOGA SUTRAS