Your tattoo does not mean "carpe diem." Those kanji are clearly a literal translation of the English phrase "seize the day," which of course means "carpe diem." "把握" means "grasp," as in to grasp something with your mind. "今日" means "today," as in "today is tuesday."
"Carpe diem" in Japanese is written, "一期一会" and pronounced, "ichi go ichi ei."
