Trying to convince others of their validity, yes - which does tend to happen for both "gnostic theists" and "gnostic atheists" - that is, theists who assert that god exists, and atheists who assert that they know that there is/are no god(s). If you're not trying to convince anyone but yourself, then you have no one but yourself to turn to for evidence, and the evaluation of that evidence is also only up to you. If you accept it, you accept it, and if you don't, you don't.
However, it is possible to point out that someone has no valid or rational basis for their belief from your own perspective (that is, lacking the personal experiences of whoever you're dealing with, and rejecting particular evidence that is not inter-subjectively verifiable) without directly taking the alternative stance. In this case, you don't have to state that "there is no god" in order to be able to point out that someone's evidence or reasons for holding a particular position are suspect.
Lastly, even if you aren't pushing your beliefs on anyone, there is absolutely nothing to stop me from evaluating your beliefs and coming to my own conclusions about the validity of your position/beliefs/ideas.