Go on, admit it. You increased your fee because you think the client is or will be a pain in the patoot.
In my experience, the relationship starts off badly and goes downhill. The client has a chip on her shoulder, demands a specific outcome, or complains about your terms of service.
No matter how hard your try, some people simply can’t or won’t be pleased.
That’s okay, because your work is not for everyone.
Spend time delighting those who want to be delighted, and ignore the rest.