I'm not sure how that's going to hurt the economy when we are looking for a deal that's more fair for us.
First, you are assuming that you are going to get a better deal. Considering how unpopular Trump in Mexico with his build a wall, there is very likely political capital to tell him in a very public way to go fuck himself. So no deal with Mexico is worse than present deal.
Second, you are assuming that deal is unfair. With US, Canada, and Mexico economies benefiting from NAFTA such view just isn't supported by facts. NAFTA is absolutely generating more trade and wealth for everyone involved. The question you should be focusing on is how this wealth is distributed internally
. This is what unfair - but then Trump's promised tax cuts would only make it less fair.
TL;DR Wrong question, wrong solution. It is like going to dentist to have your tooth removed and ending up with a prostate surgery.