It's important to be true enough to yourself because false advertising will always lead to blowback. Whether it's their disappointment (in a number of things like their perception of you and your morals for not telling the complete truth, or simply not getting what they were told they'd get) or even worse, incompatibilities that lead to break-ups. Sometimes you don't know as much about yourself and your aim in life as you should and you end up creating these incompatibilities yourself after you correct course. Life has a funny way of always punishing misbehavior, it'll catch up to you. So do some soul searching before ramifications are too big. If you already know yourself be yourself, because you want someone who wants you for you.