If you don’t feel comfortable making a rough estimate of the asset’s future earnings, just forget it and move on. No one has the ability to evaluate every investment possibility. But omniscience isn’t necessary; you only need to understand the actions you undertake.
In the quiet hours when we are alone and there is nobody to tell us what fine fellows we are, we come sometimes upon a moment in which we wonder, not how much money we are earning, nor how famous we have become, but what good we are doing.