becoming a runner

As it turns out, if I don't run for a week, what used to be easy is really hard. A month ago 3 miles was cake. Monday it was hard, today I didn't even finish. What did I do wrong?

1) I thought I could take a "break." What does that even mean? 

2) I thought I could be like my marathoner friends who run on coffee. For someone to whom running does not come like breathing, food, i.e. energy, is needed.  

3) I thought running at 9 am was a good idea. In Arkansas. In the middle of June. 

I really want to call myself a "runner," but it's really really hard sometimes. But I am lapping myself. I am burning calories and making my body work hard. It hurts, but it's super rewarding. Tomorrow *has* to be better than today. Right?