No one can guarantee to earn profit through investment. Because there are many types of risks hidden inside the investment that cannot be understood from the outside. So if I want to invest, I have to be aware of all aspects of the business that I am going to invest in and I have to invest with a long-term plan, otherwise there will be a high chance of loss after investing. I have to think ahead, never think of investing money that I can't afford to lose.
Well for it pretty simple, before ever you would even think of investment your money on anything, you would first gain ground on the knowledge of what you are about to put your hands into. I will take myself for example I have heard about bitcoin and all the benefits that follows it especially it used as an investment means but that didn't move me at all to throw my money in it so suddenly. It was not until I have properly understood the whole logic that follows a bitcoin investment and most important the capital was now available and it was three quarter of my income so I won't get affected anyway by investment that I took the step to this investment. And just like @lovemayfamilies, investment money should be somehow money which we can forget after we have invested it and I agree to this notion because you can't make an investment and you steadily panic about the investment when slight changes happens in the market.