Tu t'habillais = second person singular, imperfect indicative of s'habiller, "to dress (oneself)/get dressed."

Avec soin = with care

Tu allais = second person singular, imperfect indicative of aller, "to go."

Le lycée = French high school, to which French students can go for three years after le collège (middle school).

Tu mettais = second person singular, imperfect indicative of mettre, "to put," "to put on."

D'habitude = usuallly.

Tu as mis = second person singular, passé composé of mettre.

Ta dernière boum = your last party.