Yōga Sūtra 1.13

तत्र स्थितौ यत्नोऽभ्यासः।

[तत्र स्थितौ यत्नः अभ्यासः।
tatra = there; sthitau = steadiness; yatnaḥ = exertion; abhyāsaḥ = is practice;]

Practice (abhyāsa) is the steady exertion there (towards restraining of Chitta).

Steady i.e continuous exertion is practice. It is true for learning any new skill. E.g Playing a Guitar.