Stop in for a cup of coffee

What's everyone's rule of thumb for breaking off a sale negotiation?

I hate selling stuff to begin with... so my patience is very low.

Price + the ride
Offer
Counter offer
Agreement
Agreement, but with me paying shipping

I'm done... now I kinda don't trust you
I hate selling stuff as well. Especially trying to do something locally because I don’t want to deal with people coming to my house. I would rather keep it, instead of having to deal with all the hassle.