"That offer is too low, I'm not going to counter!"

This is a tough situation and it does happens, unfortunately, it happens often.  Now, my first advice here is to remember what the objective is-----to sell the house, key word here is house........not your home.   Sellers need to change their way of looking at their home, from the minute the sign goes in the yard, it is not their home anymore, it is a new product on the market.  So, when someone makes an offer on the house, it is not a personal comment on their home but an opportunity to sell the product at a mutually agreed on price.  You need to counter at a reasonable amount you will take and let them respond.   Remember that negotiations go both ways---they might need an earlier move in date, could be a real need for closing costs help, etc.    Never be the reason you don't find out what the buyer will actually pay.  You could be surprised and in a good way!   Bottom line, always make a counter offer!