The power of thank you notes and follow ups is substantial. If someone takes time to meet with you for your startup, career, or anything else, a quick thank you email goes far. I have met investors that use the thank you follow up as a measure of how this person treats future potential clients, customers, employees, etc.
We have busy lives, but stop what you are doing and write a thank you. Brief but honest. And if you are really smart – have something actionable included.