It makes you feel good about yourself. You feel attractive. You feel wanted. 
You feel like maybe there is just hope for you yet.

Then when you say no, you feel bad. And then you add that person to the list of people that will never talk to you again. Which makes you feel like shit.

I’m really sorry. But seriously, I have been single for 3 weeks.
I do not want to date you or anyone else.

And why the heck do you want to date me?