There's always a need of alternative plans, putting all your investment in one project means risking everything, like you mentioned what if you are not lucky and your investment failed, the outcome will ruined you financially and mentally unlike if you have other options and you managed to monitor everything the right way, if you failed from one of your investment there are other that might still going to work and will allow you to bounce back, more on how you assess and analyze its a self explained opinion I guess.
There must always be two sides that we must consider, not only considering when we can get profit, but also must consider when loss befalls us, because investment is a space full of risk, because the market is not always friendly there will be times when we will experience something bad, maybe not a loss but it will take a very long time to be able to get profit again.
dividing our money into several assets is a choice that we can do, I think I don't need to explain again what benefits we can get when doing that. Don't let us make the wrong decision, because it will determine the future of our investment.