Canto 1 - Boyhood
Bāla-kāṇḍa
Chapter 34: Satyavatī, Viśvāmitra’s Elder Sister
Text 1.34.12

अहं हि नियमाद्राम हित्वा तां समुपागतः।
सिद्धाश्रममनुप्राप्य सिद्धोऽस्मि तव तेजसा॥

ahaṁ hi niyamād rāma hitvā tāṁ samupāgataḥ
siddhāśramam
anuprāpya siddho ’smi tava tejasā

aham hi = I; niyamāt = out of consideration of the rules and regulations of yoga; rāma = O Rāma; hitvā = left and; tām = her; samupāagataḥ = arrived here; siddhāśramam = Siddhāśrama; anuprāpya = having reached; siddhaḥ = perfect; asmi = I am now; tava = your; tejasā = by prowess.

O Rāma, out of consideration of the rules and regulations of yoga, I left her and arrived at Siddhāśrama. Having reached Siddhāśrama, I am now perfect by Your prowess.

If Kauśikī is so pious and glorious, why did the sage Viśvamitra come to Siddhāśrama? That is explained here.