Here is what I consider a relapse:
First, my old thoughts and behaviors begin to occur. I'm on edge, my patience is very thin, I anger easily. I find that I begin to smoke a lot more (cigs only!) my sleep patterns become irregular. I begin to think that everyone else is wrong and I am right. Then, I begin to entertain thoughts that since I do have legitimate medical conditions that cause pain, there is nothing wrong with getting some pills to take, but only when the pain is bad. Of course, the pain really starts to get bad now. Then, I'd swallow one pill, hence I relapsed!!!!
I don't think that anyone can be going along great in their recovery, not having any old thoughts and behaviors come into play and suddenly pick up. I feel that relapse is a process, beginning with thoughts and behaviors that lead up to using.
Looking back at all of the times I relapsed after some significant amt of clean time, I can see where the above scenario played out every single time.