I mean, if a guy's a jerk and he just stays that way, isn't he being 'true' to 'himself'? Why shouldn't he? He would be being true to himself. But we don't say that. We tell him, don't be such a jerk.
So I'm officially kicking a whole phrase into the pile of meaningless words (if unexamined) such as peace, freedom, education and so forth. I assert that you should not be true to yourself unless and until you have become a better person. That means asking yourself and answering honestly what actions and beliefs will make you positively better. Before you do that, I suggest that you should not be true to yourself. A child will always a child unless he grows into adulthood. And jerks will stay jerks until they evolve past that.