Good negotiating is where both parties have an outcome that is favourable to both. The best negotiation incorporates terms and conditions (ideas) from both parties and these are the ones that stick.
When the vendor feels they have not been ‘rail-roaded’ or bullied into taking a particular offer they are more likely to stick to their acceptance with the original party, rather than continue to see what might come up next. Once you have an offer and an acceptance, it may be a week to 10 days before exchange of contracts, and in that time both parties can legally rescind their verbal agreement. In this time, if you are the purchaser you don’t want sleepless nights waiting for documents to be signed and exchanged.
If you have done your negotiating in a fair and reasonable manner, you should feel comfortable that the vendor will stick to their word and sell the property to you.