I had to take about two months off, back in the summer of 2011. When i came back, i just thought i would see where my legs would take me. What i remember most was the hell for the first couple of miles, and then having to stop. You just cant be the same runner straight away, but you have to chip away at it slowly, over a period of weeks, just taking it that little bit further every time you go out, and in between runs, making sure you stretch and look after your body.
It will come to you, but the person who will push you hardest will be yourself. I nearly quit running after my break, since it was just hell, but i forced myself to do it. So no regrets.
I am actually doing marathon training now, and there are days when i am tired, and i literally have to force myself to go out, but i do, and when i get past that first 5 i know i wouldnt want to be anywhere else, and you always feel better afterwards.