From dia and tereo; to watch thoroughly, i.e. (positively and transitively) to observe strictly, or (negatively and reflexively) to avoid wholly -- keep.
KJV: That ye abstain from meats offered to idols, and from blood, and from things strangled, and from fornication: from which if ye keep yourselves, ye shall do well. Fare ye well.
NASB: that you abstain from things sacrificed to idols and from blood and from things strangled and from fornication; if you keep yourselves free from such things, you will do well. Farewell."