"And do not lead us into temptation, but deliver us from evil." (Matt. 6:13).
Raynald III, a 14th century grossly overweight duke in what is now Belgium had a younger brother Edward who, after a violent quarrel, succeeded in having Raynald imprisoned in Nieuwkerk Castle. Built around the incarcerated Raynald was a room with near normal-sized windows and doors that didn't have a single lock or bar on them, but each one slightly smaller than Raynald's massive frame. All Raynald had to do to regain all his title and property was to leave the room -- a simple task made extremely difficult because each day Edward sent to the room a variety of delicious food. As Raynald grew fatter, Duke Edward was accused of cruelty, of which he answered: "My brother is not a prisoner. He may leave anytime he so wills."
Three truths from the illustration and above verse: First, being delivered from evil depends on not being led into temptation. They're a set. Like a front porch to a house, no trial or temptation is neutral. They're ordeals that either strengthen or weaken, depending on how they're handled. Christ teaches us to pray to be delivered from not only evil, but also from what carries us there (Jam. 1:14). Temptation isn't sin, but sin can't thrive without temptation. Or in Raynald's case, his fight wasn't in how to get through the door, but in how to get around the food.
Second, every temptation is under the direct supervision and control of God -- or the prayer (Matt. 6:13) would make no sense. The Spirit led Christ into the wilderness to be tempted, and He was delivered (Matt. 4:1). God led Ahab into temptation at Ramoth-Gilead, and he wasn't delivered (1 Kgs. 22:20). Both were under the sovereign control of God -- yet God tempted neither (Jam. 1:13). When God has a dirty job to do, He gets a dirty person to do it.
Third, if not being tempted is the optimum prayer, knowing every temptation is manageable is the optimum promise (1 Cor. 10:13). It's one thing to be left to your gluttonous self in a room surrounded by food; it's another to be there with the Spirit as a "personal trainer" helping you to refrain, showing you freedom through the windows. God's faithfulness is on the line when He promises to never allow us to be tempted beyond what we're able. What He doesn't promise is to control your lust in that temptation (Jam. 1:13-15). That depends on His mercy, which He's under no constraint to give.
Trials and temptations -- you can't grow without them (Jam. 1:2-3), and you should pray to avoid them. But once in them, prepare to "lose some weight," as God has never promised to "widen the door" (2 Cor. 12:8-9).