Simply replace the unfilled areas such as "__" and "_[date]_" with your information.
Dear _[name of date]_
I had such a wonderful time _[when date occurred, ie "last night", "Saturday"]_. I enjoyed _[name of activity included in date]_ and thought it was great that we both _[name something you had in common]_. I look forward to being able to get to know you better over future dates. I feel like we have a lot in common, and look forward to being able to share all the likes, and even some of the dislikes, with you.
Thank you for such a great time, and I hope to hear from you soon!