You may have heard it many times that we need to be true to thyself. It's totally normal if you sometimes struggle to be true to yourself because for many reasons we have to pretend. Sometimes it may seem nothing major but in many times you will feel a 'lost' feeling and you may lose the connection with thyself.
It may vary from person to person what they consider 'pretending themselves'. Because our life is so different. Many really find it difficult to be true all the time for valid reasons. But in a broader sense, if 'pretending' hampers your self-esteem, makes a negative impact on your personality and self-image then it's not a good thing as a whole.
Suppose, you don't find the same feeling for your partner but still pretend to be in love; maybe to hold the relationship. Maybe it wouldn't make a huge impact at the beginning but every single day you will feel the 'lost' feeling, you will feel your life less meaningful and lack of joy though you are doing this for better.
It's not really very difficult to find whether your 'act' makes any meaningful change or it's just creating more problems in the long run. Just give yourself some time to evaluate whether you truly reflect your emotions and feelings or not. Ask yourself questions and you will get the true answer.
Now, knowing the facts are easy but being true to ourselves is not. It needs a lot of courage sometimes to do that. And only, understanding the side effects of our 'pretending act' can help us to decide so we can make the right move!