Final answer:
The correct conjugation of lastimarse to complete the sentence is 'te lastimas'.
Step-by-step explanation:
The correct conjugation of lastimarse to complete the sentence Tú siempre _____ cuando juegas fútbol. is te lastimas. The verb lastimarse means 'to hurt oneself' in Spanish and the subject 'tú' corresponds to the pronoun 'te'. Therefore, the correct conjugation is 'te lastimas'.
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