Importance of having great co-founders

One of the main lessons learned from the speaker's startup experiences is the importance of having great co-founders. These co-founders are described as brilliant, high energy individuals who are willing to work for free and become best friends for life. The speaker emphasizes the significance of cultivating such a group as early as possible, as they will be essential in navigating the challenges and successes throughout the startup journey. The speaker credits their own success to the fact that their core team of co-founders remained with them throughout multiple startup ventures, even in their current company Evernote.