"Lead us not into temptation" (Matt. 6:13). "Watch and pray that you may not enter into temptation." (Matt. 26:41). What is temptation? It is always, in one way or another, the deception that something is more to be desired than God and his ways. Therefore, the prayer for deliverance is that we would not fall for that deception but always taste and know that God and his ways are to be desired above all others.

John Piper, When I Don't Desire God: How to Fight for Joy, p. 147

It is not enough to watch our circumstances to detect the times of temptation. We must also watch our heart to know when temptation might approach us.

We need to know our own heart, our natural disposition, and the lusts, corruptions, and spiritual weaknesses that beset us. . . . David tells us he considered his ways and kept himself from the iniquity to which he was prone (Psalm 18:23).

Just as people have differing and distinctive personalities, so they are also affected by distinctive temptations. These relate to their nature, education, and other factors. Unless we are conscious of these propensities, relationships, and dynamic possibilities, temptation will constantly entangle us. This is why it is so important to know ourselves.

John Owen, Sin and Temptation