Mesillas Yesharim 7 (Chapter 2)

"על כן יאמרו המושלים בואו חשבון"

A person must examine all his actions so he doesn't come to a bad habit (even if it is not an actual aveirah). This should be done daily, just like merchants constantly evaluate their wares. Otherwise one is likely to encounter pitfalls without even realizing they are there.

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