for you to don't regret what you've done in your life.
an auxiliary verb (abbreviated aux) is a verb that adds functional or grammatical meaning to the clause in which it appears, such as to express tense, aspect, modality, voice, emphasis, etc. auxiliary verbs usually accompany a main verb.
examples from wiki:
a. do you want tea? – do is an auxiliary accompanying the main verb want, used here to form a question – see do-support.
b. he has given his all. – has is an auxiliary used in expressing the perfect aspect of give