This is a common misconception. If the amount you invested is small enough that it doesn't matter, or that you can easily replace it, then the downside risk doesn't matter anyway.
If you wait long enough (and you should be investing for 10+ years from now) doing things that hurt growth doesn't risk you losing money, it guarantees it. And diversification hurts growth because of transaction costs.
If you wait long enough (and you should be investing for 10+ years from now) doing things that hurt growth doesn't risk you losing money, it guarantees it. And diversification hurts growth because of transaction costs.
Still, probably better to buy SPY.