Early on and first started getting them I had a lot of resentment toward them. Like others have said, I had a feeling of "punishment" involving "not going to the bathroom in a satisfactory manner," although it would have been apt due to the fact that I did withold voluntarily, and to the point of stomach cramping constipation.
As I got older the resentment diminished a lot but I never did quite offer acceptance. It didn't seem like something mom liked doing either. I was always given the chance to go to the bathroom first even during the doubling over stomach and gas pains that truly did require some kind of attention. Going to the bathroom every day like I was supposed to was the best preventive to getting an enema, and if I bitched too much in protest I'd get reminded of that.. And the fact that I was sitting on the toilet doubled over in pain because I couldn't go to the bathroom.
Eventually you developed a habit of pooping at that time of day (or so the idea went). Commonly the bulb, bag of suppository jar was left in the child's sight. I don't know if that was to "encourage" them or just for convenience of having the equipment on hand.
That ended up being pretty much my case. My "poopy time" was early evening, sometime after supper and before bedtime. It was flexible enough that I could do it so that I didn't miss certain things on tv, ect. And when I was taking a long time to do it, the disposable enema was sat on the edge of the sink (still in its box) as my usual "encouragement."