A flame is always a double-edged sword.
When putting out the ember of multiple candles by pinching the wicks between two damp fingers, the first candle may leave soot on one’s forefinger and thumb, encouraging the use of an alternate, clean finger for subsequent candles. However, the structure of the human hand is such that the thumb is uniquely necessary to the motion of pinching. These facts being what they are, an uncompromising individual who does not wish to imbibe soot may consider it viable to dampen only the clean middle finger while reusing the sooty (dry) thumb. Unfortunately, embers are not single-edged; both sides of the wick are equally capable of burning human skin.
Although the burning glow of the wick may be extinguished, the unlucky thumb will continue to register protest until it is placed in contact with an ice cube.
Lesson learned, proverb. Lesson learned.