One thing I was constantly reminded of while growing up, was to always look out for the best interests of others and not just myself. The speech I always got when I said something hurtful was "if you can't say anything nice, don't say anything at all". I think that while this is probably a pretty innocent phrase in and of itself, the context in which I received this message was that whenever I wanted to share how I felt negatively about someone, I had to sweep my feelings under the rug and just let it be. I think that my interpretation was unhealthy for my emotional growth.
As we interact with people who we don't approve of their behaviour, we are presented with a simple choice: Shelter someone from our negative feelings and say something positive yet meaningless, or be honest with them and tell them how you truly feel. The latter creates far more respect for both your audience and yourself. What self-respecting human being takes pride in hiding the truth about their feelings?
The first place to start is to be honest with yourself. Figure out what it is that you need, and be sure to communicate that with others. If you can't determine your needs for yourself, you can't go through life expecting others to know what they are either.
Relationships are built on Trust. I like to think of Trust as being at the roots of any budding relationship. It's important to start at the (below) ground level and work your way up. As with anything in life, you can't expect fantastic results at the top without a strong foundation to build on. If you can't be honest with your partner, who can you be honest with? One thing I have been guilty of in the past is lying to someone about how I truly felt just to avoid a conflict (which is also not healthy- but that's for another article).
Lying or withholding information is a short term solution and an extremely selfish move. It is both a Poison to the roots of your relationships, and disrespects your audience. It doesn't strengthen your bond. It doesn't create any sort of meaningful connection. You may not realize it at the time, but you have begun to distance yourself emotionally, it also destroys one of the roots of Trust. Eventually, I would hope that you want your relationship to blossom and produce plentiful fruit. Keep lying and eating away at those roots, and you'll be lucky to get a single leaf.