What I've recently realized:

Once you get past the number/first date phase a lot of people, myself included, slip up on the "honeymoon" phase. You clear up your schedule, ask to hang out with them on the regular, you fantasize about the person, etc.

This will get you dumped faster than saying "it's over".

The way I've combatted this is treating how much I see them as how much I'd hang out with a new friend.

When you meet a potential friend you set up a time to hang out, you don't fantasize about the future of your friendship and you make sure it naturally compliments your life. You'll go a week without contact then hit them up with a "let's grab dinner". It naturally works.

This is how you make friends and it's exactly the way you casually date someone.

The only difference is who you're having sex with. It's that simple.