Indeed. But as explained, how I live my life has no bearing on whether god actually exists or not. I cannot say that god does not exist. I live my life as though god does not, the same way I live my life as though the infinite other things I don't know about also do not exist. But that does not mean I believe them to not exist.
Actually, this depends on what you mean by "God."
The moment one uses a word, it must be the case that one means something by it, otherwise one couldn't use it.
It is imaginable to think that "God" is such that it is not possible to live one's life as if God doesn't exist.
For example, if you think of "God" as the One who makes it possible for the Sun to shine, for the atoms to interact with one another so that you can breathe air and digest food, then it is not possible to live one's life as if God doesn't exist.
Defining God as "First Cause," in a deist-like way, indeed makes it possible to live life as if God doesn't exist, given that one believes that God is the one who set the universe in motion and then withdrew from the spectacle.
But many other definitions of "God" that are available to us for consideration are such that they suggest God is involved in the details of one's daily life.
Of course, this doesn't prove that God exists, nor does it prove which definition of "God" is the right one.
But, as noted, the moment one uses a word, it must be the case that one means something by it, otherwise one couldn't use it. As long as one uses the word "God," it must be that one means something by it.
And in some cases, one's definition of "God" may indeed be in contradiction with the claim that one is living life as if God doesn't exist.
If one really wants to play it safe, one should never use the word "God" at all.