How to not feel bad when rejecting

[StarStruck]

I feel extremely bad and fragile when I have to reject a semi fat or not so good looking girl’s advances. More than I should.

Obviously some remorse is appropriate but I kind of feel consumed by it. Last week I had to do it twice and I didn’t have trouble with doing it. It is just those puppy eyes that were looking at me. 

I don’t want to be as ruthless as girls but how can I become a little more ruthless like them?