That's one lesson. Another is that if you have settled for "less than the best," explain why that is the case (e.g., 60 vote hurdle, don't want a fight, etc.).
Another is to not insult supporters who provide reasoned criticism.
Another is to be a good listener - and to be appropriately responsive, considering the merit (or lack) of the criticism.
" Another is to not insult supporters who provide reasoned criticism."
That is a good one too. Don't call those who gave you countless volunteer hours, and hundreds of millions of dollars "sexists," and "elitists."