Aim high
There aren't many unicorns out there but you're still killing yourself if you don't aim for them.
When you invest early businesses have no intrinsic value. You are buying an option. You know that most of the time you won't hit the maximum outcome, but the higher the maximum outcome the higher the option value.
To put it less mathematically, most startups won't achieve their full potential because that is hard. But the higher the maximum potential, the better the outcome for everyone even if you only hit 10% of that.
You have to start with as high a potential outcome as possible so 10% of that is a great outcome.
If you aim low, you will achieve even lower.