What does the Gita say about anxiety and worry?

योगस्थः कुरु कर्माणि सङ्गं त्यक्त्वा धनंजय ।
सिद्ध्यसिद्ध्योः समो भूत्वा समत्वं योग उच्यते ॥

yogasthaḥ kuru karmāṇi saṅgaṃ tyaktvā dhanaṃjaya
siddhy-asiddhyoḥ samo bhūtvā samatvaṃ yoga ucyate

Having recourse to devotion, O Dhanañjaya, perform actions, casting off all attachment, and being equable in success or ill-success. Such equability is called devotion.

असंशयं महाबाहो मनो दुर्निग्रहं चलम् ।
अभ्यासेन तु कौन्तेय वैराग्येण च गृह्यते ॥

asaṃśayaṃ mahābāho mano durnigrahaṃ calam
abhyāsena tu kaunteya vairāgyeṇa ca gṛhyate

Indeed, O mighty-armed one, the mind is difficult to restrain and fickle. But, O son of Kuntī, it can be restrained by constant practice and by detachment.

दुःखेष्वनुद्विग्नमनाः सुखेषु विगतस्पृहः ।
वीतरागभयक्रोधः स्थितधीर्मुनिरुच्यते ॥

duḥkheṣv anudvigna-manāḥ sukheṣu vigata-spṛhaḥ
vīta-rāga-bhaya-krodhaḥ sthita-dhīr munir ucyate

He whose heart is not agitated in the midst of calamities, who has no longing for pleasures, and from whom the feelings of affection, fear, and wrath have departed, is called a sage of steady mind.

सर्वधर्मान्परित्यज्य मामेकं शरणं व्रज ।
अहं त्वा सर्वपापेभ्यो मोक्षयिष्यामि मा शुचः ॥

sarvadharmān parityajya mām ekaṃ śaraṇaṃ vraja
ahaṃ tvā sarvapāpebhyo mokṣayiṣyāmi mā śucaḥ

Forsaking all duties, come to me as your sole refuge. I will release you from all sins. Be not grieved.