you're 23 and an 18 yr old has you by the balls.

5 years apart is a big difference at any age under 30. My rule of thumb is that stages happen every 6 years or so. for example at age 6, grade 1; at age 11, highschool is just around the corner; at age 17, graduation from highschool; at age 23, graduation from university and into the working career.

For the op, the girl and the guy are pretty much on the fringes of the stages. if she's 18 she most likely just started university/college while op has possibly begun his career. maturity levels are definitely going to differ.

I support op's decision to call it off before he gets in too deep.