What is the biggest risk a home miner often overlooks?

The risk most home miners underestimate is not price; it is concentration on one variable. They lock in expectations based on today's MLRT price, today's difficulty, and today's electricity rate, then act surprised when any of those move. A realistic plan treats all four mining variables as moving targets and stays solvent if any one of them turns against you. Hardware wear, summer cooling costs, and the time you spend tinkering are real expenses too. The goal is to be able to walk away from mining at any point without feeling like you have to recover sunk costs. If you cannot, you have over-committed.