One of the biggest mistakes I made going in, was thinking meditation was about blocking everything unnecessary out.
I thought there was one "President" thought that could drive out all the others. I was wrong. Now, for me, meditation is about hearing everything going on around you.
Desire
I think of the example that many Buddhists follow. In Buddhism, one should not desire. But then the person has the desire to not desire.
So, people think they aren't suppose to think, so they have a principle thought that tells them not to think. Which, in hindsight does not make much sense.
Buddha only taught one single universal Truth: unfullfilled desire causes frustration and the rejection of frustration is the source of suffering.
So, when you desire something, and don't get it, you can get frustrated. And when you don't acknowledge the frustration, that is where suffering occurs.
We don't always get what we want. A lot of times, it seems that if we don't get something we say "Oh, I didn't want that anyways." In some cases that may be true, but for many, it's not. It's a coping mechanism to make us 'feel better', when really, internally we are suffering. And we suffer a great deal more (maybe not at that instance, but more down the line) when we don't acknowledge that.
Dealing with Reality
So, for me, meditation is about acknowledging the presence. Not about shutting it out or ignoring "bad sounds" (like someone coughing, or dropping a pen). It's about hearing everything. And after a while, your body will get 'bored' and achieve a higher state of consciousness, which is what we call 'meditation'.
When you start acknowledging things, you come in closer to reality. And when you deal with reality, that is when you can actually make progress.
That's why being in denial is harmful, because you aren't acknowledging what is actually happening. So then you don't deal with reality, and you can't use the circumstances that you are in to grow.