I've only asked for a raise with an insecure voice and shaking hands because two weeks ago a client sent me a critical email so therefore I am not doing my job very well am I?

Yeah. Right.

Now I'm a freelancer and just decide my fee and if it's too high for the client he/she will have to find someone else. Because I only 'sell' what I know I'm good at. It has helped me a lot finding security.

If this is the kind of content you'll be writing I'm going to have a lot of fun reading you, thanks! :-)