Gold miners are like stamp or coin collectors, in that when they find a nugget or two they know they have a valuable specimen. Like philatelic or numismatic collectors, gold miners recognize and value their rare 'special' find. Hunger and human need being what it is, they must sell their gold for immediate profit at today's prices in order to meet today's needs.
Being a successful gold miner requires being lucky enough to find enough gold to more than satisfy today's need. Being successful requires knowing enough to resist the temptation of want over need. To be successful, the gold miner must know where and when and how to invest the excess over need, to invest the amount that more than satisfies today's need.
Consider: It requires some amount of knowledge regarding how to find gold, how to assay a 'find', how to retrieve all of the mineral once discovering its location. However, having all of this knowledge does not attract luck. Luck is where you find it. Some people are lucky, some are not, but without that special knowledge concerning gold, one might walk over a likely spot and entirely miss a lode. If there is any 'bad luck' in such an instance, it is relegated to the missed opportunity to gain the knowledge - not to stepping blindly on the gold without seeing it or failing to suspect its presence.