A crypto miner’s tendency to withhold a newly generated block from the main blockchain to earn more than other miners.
Selfish mining is a fraudulent act that a miner engages in to withhold a newly generated block from the main blockchain. The miner does this so that they can gain more rewards and stay ahead of other miners. This eventually alters the blockchain and damages the prestige of cryptocurrency.
When they make new blocks available in their private network after withholding new blocks, miners inadvertently cause the value of the cryptocurrency in question to diminish. Hence, miners engaging in selfish mining are always advised to desist from it since it also affects them negatively.