You are who you are.  You have essentially been this person your whole life, and you will essentially be this person for the rest of your life.  So why would you try and pretend to be someone else?  To make someone happy?  I don't think so.  There are several possible bad side-effects of this behavior, but there are two things that will certainly happen.  First, you will be miserable, and second, the relationship will not stand the test of time.

You will be miserable - Imagine waking up in the morning, looking in the mirror, and wondering who that stranger is looking back at you.  That's what it's like when you pretend to be someone you are not.  Almost everyone has hopes and dreams from a very young age.  They may change slightly as you get older, but fundamentally they are the same.  These hopes and dreams are a major part of who you are.  You will basically be living someone else's life, not your own, if you pretend to be someone you are not.  Not only will this make you very unhappy, but it will wreck your relationships as well.

The relationship will not last - By being someone that you are not, you have basically turned the relationship into a ticking time bomb.  At some point, one of two things will happen.  Either you will get tired of pretending, and you will begin to act like someone that your partner doesn't know (or doesn't like), or your partner will see through your facade, and get tired of the fact that you are not genuine.  Either way, it is terribly unfair to both parties, and will undoubtedly cause major bad blood between the two of you down the road.

So, do yourself (and your partner) a favor.  Be yourself and don't change in an attempt to make someone else happy.  If they don't like the person you are (or vice versa), you don't belong together anyway.

This article is an excerpt from the book Missing Pieces: 21 Secrets of a Successful Relationship by Will Irvin, now available from Lulu.com in paperback, hardcover, and for download.