This is about how hard it is to win over a competitor with an already established relationship with customers.
What does "pounding" mean here? It's translated as "make an effort".

ex)Sometimes, no matter how hard we try, we lose because someone else arrived there before us. Suppose I open a grocery store. People tell me that though they like what I do, they buy from the other guy's grocery store because he's been good to them...And even then they'd probably give him a second chance, because forgiveness is the hallmark of a good relationship. If I kept pounding, I might be able to win a percentage of my competitor's business...