A lit match, when blown on even slightly, is extinguished. However, with a coal, the more that one blows on it, the greater the fire becomes.
The reason for this being, that with the match the fire is external, and in the coal the fire is internal.
The same is with man. When our passion to connect to G-d is external, even the slightest distractions will extinguish our flame. If, though, our fervor is internal, disturbances will only make us stronger.
(L’maan Yeidu..Banim Yevaleidu, Pg. 294)