Have you ever kissed someone and ...?

It happens to me and I'm 35! I think you nailed it, it's your conscience at work inside your head. I think it shows #1 that you really like this guy and it's probably worth continuing to find out if a relationship would work out, but also that you are conscientious enough to make sure that YOU come first (meaning, your education, your age, probably other factors) and that was a great decision. It's very normal, it's healthy, and I'd take note because it very well could happen again. Be proud of the fact you used restraint; not many folks do! Good job!!