No vs. Yes
Saying no - one of the more difficult things to do in a service business.
The reason being the obvious one is that you want to make sure they are ‘happy’ with your service and keep giving you opportunities for business.
The confidence it takes to say no comes once you realize that the best thing you can actually do for the client is to their request down and guide them to a better outcome for them.
Obviously, not all clients appreciate being turned down and some will leave and not come back. But those that understand why you are saying no and that you have a better outcome (for them) in mind will become your most loyal customers.
Years ago I was running a small consultancy where my mortgage was at stake on occasion. The courage I developed by saying no when I really needed the money is now serving me (and the people whom I've worked for) better than any other skill.
My team was happier. We did not have to deal with challenging (some would say, unreasonable clients). We were working on things where we could actually succeed (instead of accepting assignments we know going index can’t do well, but we do it for the money)
And most importantly seeing the (perhaps newfound) respect clients had for our profession when we said: ‘Sorry, in our opinion your request is not in your true best interest and we have to say no thanks.’
Integrity is too big a word for this, it is ‘just’ doing what makes the most sense for the client and thus for you since you are in the client service business.