You can download these cards from The Really Big Questions. The first six were written by Esquire's AJ Jacobs, while the others come from PRI fans. Feel free to offer up your own rational Valentine's Day messages in the comments below.

1. You light up my prefrontal cortext.

2. The pros of being with you outweigh the cons.

3. You are one of several thousand people who could make a compatible partner for me.

4. I will always be true to you because having an affair sounds exhausting.

5. I love you as much as a praire vole loves its mate.

6. Please settle for me. I've settled for you.

7. So far. So good.

8. I believe our relationship is mutually beneficial.

9. I could tolerate you for a lifetime.

10. I give you this document to acknowledge that we are in a relationship and I anticipate that it will continue.

Feel free to offer up your own rational Valentine's Day messages in the comments below.