Unless you work in demolition, don't burn bridges.
The sale begins when the customer says yes.
I've known entrepreneurs who were not great salespeople, or didn't know how to code, or were not particularly charismatic leaders. But I don't know of any entrepreneurs who have achieved any level of success without persistence and determination.
Say and do what you mean, but never say and do it meanly.
Make the second effort your second nature.
The quality of your life is determined by the quality of your relationships. The quality of your business is no different.