Are you referring to new customers or ones you have had for some time?
It is human nature that we tend to look at the faults of others, rather than focus on what is good in people.
Trust does take a while to build, but once you have done it with your customers you will feel a lot more positive, because they will show it by the way they treat you, leading to your feeling better about them and yourself. Not everyone will respond, but the majority will, and they will be the good customers you will want to keep.
John