For a Starting Ecom owner (in the Sustainability & Organic Product Industry) What are some of the Biggest Mistakes you made that You learned from and helped you?

I'd love to know, from those people who are more established in this industry of online store-running.

It would be great to have some food for thought on what you think are some huge errors that can catch up to you in the long run if you're not aware or what you think are essentials to keep an eye on when thinking long term about running an Ecom store?

Thanks for your time.