For some reason, the common wisdom goes that if you work for a client, your creative voice doesn't matter. That could not be further from the truth. Creative people are paid to have unique voices. A voice is the creative person's differentiator. And we all know how important it is to differentiate yourself.
Businesses pay a creative person or agency to express something that they themselves cannot. They don't have the know-how. Often they don't even know what it is they are trying to say. That is okay. They probably don't wake up every morning thinking "what is it that I am trying to say here?" They are not used to this type of thinking. Their worry is day-to-day operations.
Creativity is all about making decisions and making good decisions takes creative thinking. An you know who does creative thinking full-time? That's right, the creators.
Why would you be the best person to do an identity project for the client X? Well, because your creative voice matches what the client is trying to say. Your voice is the embodiment of client X's vision. It gives concrete sights and sounds to the image of what your client is trying to portray. What is the point to give you the project X if the client can't tell your voice apart from the next person? How would they know what look and feel will you give them.
I know you will say that a good designer should be a good chameleon and adapt to the client needs. That is true. But I am not talking about just how things look. If you are able to justify your creative decisions every step of the way, you are doing it anyway — you are really designing how things work. And this is what good design is about.
Having a voice takes practice, and practice is doing all kinds of things that let you develop your voice — doing art projects, writing, soul-searching, protesting, serving a cause, there are plenty of ways to develop your voice out there. Not exercising your voice enough is like not being very fit while having a physically demanding job. If you can't lift heavy things you won't be very useful working as a loader in a warehouse.
So if you are paid to make creative decisions developing your voice should be high on your priorities list.