Trouble releasing entire coffee enema

I tried a coffee enema for the first time yesterday. I encountered the same problem I have encountered in the past whenever I have taken enemas of any kind - and this problem is the reason I seldom ever have taken enemas - I could only release part of it when it was time. About half an hour after that, I could release some more coffee, then in another hour, some more. But some of the coffee just stayed in there. Is that harmful? Why is this happening to me?

Normally, I tend to have a very sluggish bowel. The urge is weak and fleeting. I don't have "hard, dry stools" so I don't know whether to call it "constipation." I just always kind of feel like my colon is full, there is little or weak propulsion, and it's very uncomfortable.

When I took the coffee, though I hadn't taken an enema in years, it was very easy to take the entire quart and hold it for 15 minutes. I could have held it for hours. All the accounts I've heard talk about the struggle people have to take the whole quart and hold it the whole time. What is up with me??