Our natural impulse is to stay as close to the one we love as possible, especially when we're trying to make sure that we continue to be his future instead of somebody else that catches his eye...
so more than any other time in our lives, our panic reflexes kick in and we end up clinging to our exes, which only causes more trouble than you already have.
There are a number of dire consequences to living this way, not the least of which is the clear fact that you end up looking incredibly desperate.
  Even if you are to a degree, you can't let that be obvious or else you'll look horribly unappealing and there's no way he'll want to get back in the middle of things.
A number of other mistakes that can have too-high costs are only made easier when you're always in contact with him...
such as phone-based oopses like Text Message Terrorism and Drunk Dialing.
  For more detailed explanations on these mistakes, click the link in the last paragraph, but for the moment rest assured that these are something you want to avoid.
And, as you may have guessed...
being so close together after and during such an intense emotional time can lead to a lot of anger and resentment flaring up, making things exponentially worse and potentially ruining your chances to get him back.
  Truth be told, this isn't even everything that could go wrong, and a lot more probably will if you allow yourself to be in too close of contact with your ex after the breakup.