Adam Clarke on Revelation 3:2

Be watchful - Ye have lost ground by carelessness and inattention. Awake, and keep awake!

Strengthen the things which remain - The convictions and good desires, with any measure of the fear of God and of a tender conscience, which, although still subsisting, are about to perish, because the Holy Spirit, who is the author of them, being repeatedly grieved, is about finally to depart.

Thy works perfect - Πεπληρωμενα· Filled up. They performed duties of all kinds, but no duty completely. They were constantly beginning, but never brought any thing to a proper end. Their resolutions were languid, their strength feeble, and their light dim. They probably maintained their reputation before men, but their works were not perfect before God.