Massive Trading Mistake Could Reduce Your Earnings to Nothing

Many finance experts tell investors that they should avoid

.

They also say that investors shouldn't trade when they are tired or distracted, among other common tips. That is sound advice, but there is one important tip that is always missing. "I always encourage people that if they're going to trade, at least try to have a second income stream," Don Miller, author of

, told Benzinga. "Whether it's another job outside of market hours or a spouse's income or a significant other's income, real estate income, investment income, part-time consulting in your own industry -- find something that will allow yourself to cherry pick opportunities."

Miller said that investors should never force a trade. "That was a huge lesson I learned," he said. "If I were to do it over again, I would have made sure that I had a separate income stream when I went at this. I didn't do it. Huge, huge mistake. "When you're trading part-time and you have another income stream that pays your bills, it's a lot different. You can pick your stocks, you can pick your opportunities. It's like a professional golfer in the PGA tour -- if every crumb that goes on the table is going to be dependent on this next putt, that's a h*** of a lot different than having somebody sponsor you and pretty much pick up your expenses." Miller said that trading is very similar. "When I was doing it part-time, I had a really consistent streak of profitability," he said. "When this is all you do and you're on the market for…it's more than eight hours with the global markets. You could be trading for 15 hours a day. And all of a sudden it's, 'I gotta trade, gotta trade, gotta trade.' You start forcing things. You get away from what made you successful to begin with. I did that -- I broke every rule in the book because I was on the market all day long. I had time to break rules. I had time to over trade. I had time to take marginal opportunities." Miller ate through his "entire earnings accumulation in a month." "That was maybe four to six months of profit," he said. "So that was a huge mistake."