The sages tell us that out of one thousand students who embark on the path of Torah study, only one emerges worthy of rendering halachic decisions [Vayikra Rabbah 2:1]. Hashem endows some people with more natural gifts - such as superior intelligence and less of a propensity towards being distracted - than others.
Natural abilities are like a fire: if they're misdirected they become destructive.
Yichus is also a gift of fire. Torah is the vessel that can safely handle the fire, but if someone doesn't have Torah, then all his inherited talents and energy become a fire than can consume him. If he doesn't use his fire for Torah, then it will be used for other things, or will ultimately consume the person himself.
Source: Rabbi Mendel Kaplan
"Reb Mendel and His Wisdom" by Yisroel Greenwald