The phrase "slips up" means to make a mistake or error, and can be used in various situations such as in sports, work, or personal life. When we talk about antonyms for this phrase, we are referring to words that describe actions that are opposite to slipping up. Some of the antonyms for "slips up" include excels, succeeds, accomplishes, gains ground, progresses, advances, and achieves. These words imply a sense of achievement, progress, or success, as opposed to an error or mistake. Thus, if we want to avoid slipping up, we must strive to excel, succeed, and progress in our endeavors.