Anyone who has done any level of carpentry or even DIY will understand the benefits of measuring more than once in order to make the cut right first time.
The equivalent in business is to make mistakes on your business plan.
Try things out on paper, excel or one of the brilliant forecasting apps that allow you to run different scenarios. Make any mistakes at this stage rather than running out of cash in real life.
For instance, I allow 3 months for a new team member to get up to speed. During this training period my own productivity will also drop so I now build this into any of my forecasts.
What other scenarios are you considering in your future business?